switch back to original sexpr usage of PTREE, add new DSNLEXER constructor, enforce accessors in kicad.exe

Pspice netlist generator: add option to use net numbers as net names (feature removed a long time ago, but needed by Oscad team)
Note these options are saved in project config.

2) Change from legacy Cu stack to counting down from top=(F_Cu or 0).
   The old Cu stack required knowing the count of Cu layers to make
   sense of the layer number when converting to many exported file types.
   The new Cu stack is more commonly used, although ours still gives
   B_Cu a fixed number.
3) Introduce class LSET and enum LAYER_ID.
4) Change *.kicad_pcb file format version to 4 from 3.
5) Change fixed names Inner1_Cu-Inner14_Cu to In1_Cu-In30_Cu and their
   meanings are typically flipped.
6) Moved the #define LAYER_N_* stuff into legacy_plugin.cpp where they
   can die a quiet death, and switch to enum LAYER_ID symbols throughout.
7) Removed the LEGACY_PLUGIN::Save() and FootprintSave() functions.
   You will need to convert to the format immediately, *.kicad_pcb and
   *.kicad_mod (=pretty) since legacy format was never going to know
   about 32 Cu layers and additional technical layers and the reversed Cu
   stack.

They are now member of EDA_DRAW_FRAME.
This change could fix Bug #1330781 (Background color change in Eeschema affects background color in Pcbnew)
Show page limits has meaning only for the schematic editor,  the board editor and the page layout editor.
Draw background color selection exists only in eeschema and  page layout editor.
In pcbnew, only a black background is allowed.
A side effect is now the user should set the background color in schematic editor, and the library editor (2 different options).
The default is still the white color.

- Refactored the common part of cursor key movement and crosshair update
  in the various GeneralControl
- Add x10 movement with the keyboard (CTRL modifier)
- Avoid fixup of the cursor position by dummy mouse movements generated
  by cursor warping (original analysis and idea Chris Gibson)
- Do key handling in a way to permit sub-pixel cursor movement 

Change class PROJECT to use a generalized wxString in place of the
RETAINED_PATH items, so that new session and project specific strings
of any purpose can be saved there, for the life of a session.

Fix segfault when deleting last user path from eeschema libpaths and then pressing cancel.

remove global g_UserLibDirBuffer which was a project specific global, and no longer used with FP_LIB_TABLE support.

Made the project default text size apply to all text things in eeschema, instead of the hardcoded value

DXF export: fix incorrect export of polygons having thick outline (like zones): Thick segments of outline were drawn like lines with no thickness.
Fix ( workaround only) crash (Windows only) when a quasi modal frame (like footprint viewer) was called from a dialog (like the component properties dialog in schematic editor).
Very minor other fixes.

- Better shape to the 60617 pin markers
- Made the markers' size proportional to the pin text
- Added the missing implementation in the pin plot routines

fix also a bug in python script round_value_robin.py.

fix also a bug in python script round_value_robin.py.

*) Eeschema can now show the footprint editor.

*) Eeschema can now invoke the footprint picker from the library part field editor.

*) KIWAY_PLAYER::ShowModal() takes aResultantFocusWindow that tells what window
   to give the focus to.  Required since frames are often near the top of the
   hierarchy and they are invoked by a peer, not a parent.

*) Eeschema can now show the footprint editor.

*) Eeschema can now invoke the footprint picker from the library part field editor.

*) KIWAY_PLAYER::ShowModal() takes aResultantFocusWindow that tells what window
   to give the focus to.  Required since frames are often near the top of the
   hierarchy and they are invoked by a peer, not a parent.

Kicad: fix crash on exit, when Libedit was called during a session. It fixes also a crash if Libedit was called, closed and reopened.
Happens only if eeschema was called from the Kicad manager.

Kicad: fix crash on exit, when Libedit was called during a session. It fixes also a crash if Libedit was called, closed and reopened.
Happens only if eeschema was called from the Kicad manager.

*) KIWAY_PLAYER::IsModal() is now a retained state, controlled by SetModal()

*) Fully re-work the KIWAY_PLAYER::ShowModal() to use a nested event loop.

*) Add support to DIALOG_SHIM for a "quasi-modal" dialog presentation and mode.
   See top of dialog_shim.cpp about that for benefits and need.

*) You can now pick footprint from the schematic component field dialog, although
   if you do this before you open the BOARD, you will only get the global footprint
   libraries, not also the project specific ones.  Opening the BOARD first avoids this
   problem.

This is the first example of cross KIFACE invocation, it is also the first
instance of using a TOP_FRAME other than FRAME_PCB as the first thing. It works,
but it's missing support for opening the project specific table because
historically the FRAME_PCB did that. This is now starting to expose all the near
term needs for KIWAY_PLAYER <-> PROJECT interaction, independence and out of
sequence usage.

A fix for this will be coming in a few days.

However it mostly starts to show why the KIWAY is terribly useful and important.

*) KIWAY_PLAYER::IsModal() is now a retained state, controlled by SetModal()

*) Fully re-work the KIWAY_PLAYER::ShowModal() to use a nested event loop.

*) Add support to DIALOG_SHIM for a "quasi-modal" dialog presentation and mode.
   See top of dialog_shim.cpp about that for benefits and need.

*) You can now pick footprint from the schematic component field dialog, although
   if you do this before you open the BOARD, you will only get the global footprint
   libraries, not also the project specific ones.  Opening the BOARD first avoids this
   problem.

This is the first example of cross KIFACE invocation, it is also the first
instance of using a TOP_FRAME other than FRAME_PCB as the first thing. It works,
but it's missing support for opening the project specific table because
historically the FRAME_PCB did that. This is now starting to expose all the near
term needs for KIWAY_PLAYER <-> PROJECT interaction, independence and out of
sequence usage.

A fix for this will be coming in a few days.

However it mostly starts to show why the KIWAY is terribly useful and important.

In particular HitTest for zones *do not* select the nearest vertex/edge as a side effect

In particular HitTest for zones *do not* select the nearest vertex/edge as a side effect

*) Rework the set language support, simplify it by using KIWAY.  Now any major
   frame with a "change language" menu can change the language for all KIWAY_PLAYERs
   in the whole KIWAY.  Multiple KIWAYs are not supported yet.

*) Simplify "modal wxFrame" support, and add that support exclusively to
   KIWAY_PLAYER where it is inherited by all derivatives.  The function
   KIWAY_PLAYER::ShowModal() is in the vtable and so is cross module capable.

*) Remove the requirements and assumptions that the wxFrame hierarchy always
   had PCB_EDIT_FRAME and SCH_EDIT_FRAME as immediate parents of their viewers
   and editors. This is no longer the case, nor required.

*) Use KIWAY::Player() everywhere to make KIWAY_PLAYERs, this registers the
   KIWAY_PLAYER within the KIWAY and makes it very easy to find an open frame
   quickly.  It also gives control to the KIWAY as to frame hierarchical
   relationships.

*) Change single_top to use the KIWAY for loading a KIFACE and instantiating
   the single KIWAY_PLAYER, see bullet immediately above.

*) Add KIWAY::OnKiwayEnd() and call it from PGM_BASE at program termination, this
   gives the KIFACEs a chance to save their final configuration dope to disk.

*) Add dedicated FRAME_T's for the modal frames, so m_Ident can be tested and
   these modal frames are distinctly different than their non-modal equivalents.
   KIWAY_PLAYER::IsModal() is !not! a valid test during the wxFrame's constructor,
   so this is another important reason for having a dedicated FRAME_T for each
   modal wxFrame.

On balance, more lines were deleted than were added to achieve all this.

*) Rework the set language support, simplify it by using KIWAY.  Now any major
   frame with a "change language" menu can change the language for all KIWAY_PLAYERs
   in the whole KIWAY.  Multiple KIWAYs are not supported yet.

*) Simplify "modal wxFrame" support, and add that support exclusively to
   KIWAY_PLAYER where it is inherited by all derivatives.  The function
   KIWAY_PLAYER::ShowModal() is in the vtable and so is cross module capable.

*) Remove the requirements and assumptions that the wxFrame hierarchy always
   had PCB_EDIT_FRAME and SCH_EDIT_FRAME as immediate parents of their viewers
   and editors. This is no longer the case, nor required.

*) Use KIWAY::Player() everywhere to make KIWAY_PLAYERs, this registers the
   KIWAY_PLAYER within the KIWAY and makes it very easy to find an open frame
   quickly.  It also gives control to the KIWAY as to frame hierarchical
   relationships.

*) Change single_top to use the KIWAY for loading a KIFACE and instantiating
   the single KIWAY_PLAYER, see bullet immediately above.

*) Add KIWAY::OnKiwayEnd() and call it from PGM_BASE at program termination, this
   gives the KIFACEs a chance to save their final configuration dope to disk.

*) Add dedicated FRAME_T's for the modal frames, so m_Ident can be tested and
   these modal frames are distinctly different than their non-modal equivalents.
   KIWAY_PLAYER::IsModal() is !not! a valid test during the wxFrame's constructor,
   so this is another important reason for having a dedicated FRAME_T for each
   modal wxFrame.

On balance, more lines were deleted than were added to achieve all this.

Eeschema: fix unwanted creation of noname.pro (or other useless config file), when opening eeschema. Fix also an issue when saving the config (from save config menu) which saved the config file in an unknow folder.

Eeschema: fix unwanted creation of noname.pro (or other useless config file), when opening eeschema. Fix also an issue when saving the config (from save config menu) which saved the config file in an unknow folder.

- Converted the Next/Prev C casts to static casts and removed the type
  unsafe ones
- Splitted as virtual the VIA::Flip member instead of using RTTI
- Heavily refactored the 'unconnected track' cleanup routine
- Misc constification

Plots function: fix a bug about virtual PLOTTER::Text, which was not virtual for derived classes due to a missing parameter in ::Text in these classes. Noticeable only in SVG plot.
SVG plot, fix a missing reinitialization in plot lines, which could define a filled polyline, instead of a simple polyline
(these fixes solve Bug #1313084 )

eeschema: fix the very minor bug  #1298094. But it was due to a bad bounding box calculation, which is now fixed.