Some minor code cleaning.

Enhancements in AddMenuItem (that accepts now a menu type)
Partial use of the Edwin van den Oetelaar's patch (patch not fully working or correct)

Instrument saveNETCLASS() with fmtBIU().
Can now round trip to mm board file using LEGACY_PLUGIN in DEBUG build.

* Save dialog now supports saving boards to new file format.
* Add CMake option to build s-expression file save.
* Add check to main CMakeList.txt file to make sure nanometers are
  enables when the new file format is built.
* Minor tweaks to object format functions for improved output.
* Rename kicad_plugin.h/cpp to legacy_plugin.h/cpp.

* Add s-expression Format() function to all objects derived from
  BOARD_ITEM.
* Add s-expression Format() function to base objects as required.
* Add functions to convert coordinates from base internal units
  (nanometers) to millimeter string for writing to s-expression
  file.
* Add temporary dummy conversion functions to prevent link errors
  until schematic and board object and action code can be separated
  into DSO/DLL.
* Add CMake build option to build Pcbnew with nanometer internal
  units.

* BLOCK_SELECTOR class is not longer derived from EDA_ITEM.
* Encapsulate BLOCK_SELECTOR class member variables and add access methods.
* Move HandleBlockBegin() function from block_commande.cpp to drawframe.cpp.
* Remove virtual methods from top level derived objects per future
  coding policy change.
* Remove Doxygen copydoc statement from objects derived from EDA_ITEM
  since the comments are automatically copied to the derived object.
* Removed copy and pasted Doxygen comments from objects derived from
  EDA_ITEM.

class EDA_RECT: is no more derived from EDA_ITEM, just from EDA_RECT (reason: does not use anything in EDA_ITEM)
issue in cast to wxRect fixed (EDA_RECT accepts negative size, but not wxRect, so the wxRectcast  is normalized now).
This fixes some bugs.
A minor other bug fix in Pcbnew.

Add include/dialog_shim.h and common/dialog_shim.cpp for use by wxformbuilder's "subclass a wxDialog" support.
This works, but in my version of wxformbuilder there is a bug which does not properly show the 
subclass property, even though it is still in play.  This happens after saving then loading the *.fbp file.
So it is a nuisance bug, but does not affect functionality.

Remove 2 duplicate icons.
Minor cosmetic enhancements and fixes in popup menus.

Eeschema: fix a bug in bool SCH_LINE::MergeOverlap( SCH_LINE* aLine ): ends point of resulting segment incorrects.
remove unused icon files.

* Remove double Clone() function calls from all classes derived from
  EDA_ITEM.
* Lots of Doxygen comment warning fixes.

* All objects derived from EDA_ITEM now have consistent hit test method
  definitions.
* Remove double function calls from all classes derived from SCH_ITEM.
* Lots of Doxygen comment fixes.

* make 2 bitmaps more visible.
* fix incorrect screen redraw when rotating a component.
* netlist : the pcbnew advanced format can be now stored (persistant option) in project config.

  * Save all visibilities, layer and render, in BOARD and restore on load.

Pcbnew:
 * graphic_item_properties_base.fbp * dialog pad edit: make some strings more easier to translate.
 * global pad edition: fix a bug that change pad position instead of pad size (round pas only).
Eeschema:
 * fix a bug: new created wires were not alwaes shows until the screen was redrawn.

All: added a standard exit dialog called by int DisplayExitDialog( wxWindow* aParent, const wxString& aMessage )
Called when closing pcbnew, cvpcb and eeschema.
Minor code cleaning: remove duplicate or not used strings (mainly file extensions and wildcards)

wxWidgets 2.9 knows wxSVGFILEDC device context.
Unfortunately, arcs are drawn as pies (this is a feature, not a bug).
This is not correct for Kicad.
So Kicad has its own wxSVGFILEDC (named KicadSVGFileDC) that is basically the same as wxSVGFILEDC,
but with arcs drawn as arcs, not pies.
Note also under wxWidgets 2.8 does not know wxSVGFILEDC , so kicad had already its own SVG device context.

Pcbnew: Hight contrast mode: commit last patch from Miguel Angel Ajo Pelayo, which also  fixes an old bug.
All: prepare better compatibility with wxWidgets 2.9.4. Works fine with 2.8.x (I hope...)

ModEdit (and ModView): make "invisible" texts visible. They are not visible in  the board editor, but must be visible in the footprint editor.
Minor doc update.

* Convert Eeschema from manually linked list to DLIST for storing
  SCH_ITEM objects.
* Add helper functions to SCH_SCREEN for appending list of SCH_ITEM
  objects.
* Fix bug in wire editing code for accurate undo/redo behavior.
* Add member to DLIST to append another DLIST.
* Other minor code cleaning.

Eeschema: Viewlib is now accessible from Libedit (to browse libs or load a component to edit)
Libedit: uses now the same dialog as the schematic editor to load a component
Some code cleaning.

Code cleaning and other minor fixes.

 * Added a dialog to select options: one or 2 files, units (mm or inch), and force INSERT option.
 * code cleaning
 * Modify corresponding  icon in menu to show a footprint, not a schematic component.

Icons for modedit and modview: remove unused or duplicate icons files and rename files. Tweak some icons.

Pcbnew: Added: modview. This footprint viewer frame which has the same purpose as Viewlib in Eeschema.
this viewer is built using the new  FOOTPRINT_VIEWER_FRAME class.