Temporarily disable Boost.Context library build as it breaks MinGW builds by bringing in a dependency on MASM (The Microsoft Assembler)

Planning for PCB_BASE_FRAME::Save_Module_In_Library and PCB_EDIT_FRAME::ArchiveModulesOnBoard rewrites

Pcbnew: Fix issue when displaying net names and/or pad numbers including the "<" char in drc dialog, because drc dialog uses an wxHtmlWindow to display drc messages, and the "<" char has a special meaning and is not allowed in texts (now replaced by the" &lt;" sequence in messages displayed in html)
Eeschema: replace "<" and ">" by "(" and ")" in autogenerated net names, to avoid other issues in html messages.
Very minor other fixes.

*) Set environment variable KISYSMOD before loading FP_LIB_TABLE so that
   FP_LIB_TABLE::ROW::SetFullURI() can do substitution up front.
*) De-emphasize the lib path in some of the footprint frames but keep it
   so the footprint editor can export a current library to another.
   You can even export a GITHUB library to a pretty library for local 
   installation.
*) Start the PLUGIN options editor.
*) Enhance cursor positioning in DIALOG_FP_LIB_TABLE.

specctra_export.cpp: fix a bug in my export function to 3D viewer which generates bad shapes for holes generated by outlines
inside the main board outlines.
specctra_export.cpp: always approximate arcs in outlines by 36 segm for 360 degrees,
even for arc angle which differs from 90 degrees.
90 degrees is the default when creating an arc, but the arc value can be edited and have any value between 0 and 360 degrees.
Previously, 9 segments were used regardless the arc angle.

* Add save table and set project path environment variable code to
  FP_LIB_TABLE object.
* Add code to Pcbnew and CvPcb to set project path environment variable.
* Create empty footprint table in Pcbnew when new board created.
* Save current project specific footprint library table to path on file save
  as or empty project path.
* Fix a bug in Pcbnew in file save function that would silently overwrite
  an existing board file.
* Disable selecting the current library in the module editor when there are
  no libraries defined.
* Catch exceptions and report errors when writing footprint library tables.
* Fix Boost build CMakeFile to fix bug when bootstrapping a Boost build in
  MSys.

Remove wxUSE_UNICODE definition from CMakeLists.txt, because this define comes from wxWidgets and should not be made inside kicad
Remove KICAD_GOST option because it is  now useless: the 2 GOST options are now selectable at run time and are:
* specific page layouts (now user definable, and the GOST page layouts are available in template folder)
* notation for multiple parts per package (made in eeschema, preference menu)

* Pre-built binaries for OpenSSL can be used from the LuaDist project: https://github.com/LuaDist/openssl/releases
* Building of Boost libraries fixed for Mingw-w64 for github plugin

* Don't convert footprint library path to wxFileName.  This removes a '/'
  from the GIT_HUB_PLUGIN uri which causes wxUri to choke and the incorrect
  plug in is selected.

We can now remove a few calls to FP_LIB_TABLE::ExpandSubstitutions( const wxString& aString )
since its being done in above function.

DIALOG_FP_LIB_TABLE now handles table to copy cut copy paste from global to
project and reverse.  Fixed a problem with cursor position management when
switching between tables.

Put FP_LIB_TABLE::Footprint*() functions on stage, but comment out lazy plugin lookup trick in FindRow() until these new API functions are used.

CTL+X, CTL+V, CTL+A, CTL+C

Remove tooltips from fp_lib_table wxGrid, were annoying and munging wxGrid's grid.
Change initial size of DIALOG_FP_LIB_TABLE.

3D viewer: Preference menu: fix a bug which displays incorrectly the actual display options state (always shown off) when starting the 3D viewer

3D board display: better rendering of the board: the board polygon outlines (generated by the specctra function which calclaltes outlines) is now used to create the 3D body of the board,
in pcbnew and cvpcb.

Move specctra.cpp, specctra_import.cpp and specctra_keywords.cpp compilation to pcbcommon lib because they containt functions used by the 3D viewer in Cvpcb and Pcbnew.

3D board display: better rendering of the board: the board polygon outlines (generated by the specctra function) is now used to create the 3D body of the board.

Removed some Microsoft Visual C centric definitions in CMakeModules/config.h.cmake which were tripping up the mingw-w64 build

Paste popup menu in this dialog now allows pasting a (fp_lib_table)
s-expression element holding (lib) elements.  This provides an 
opportunity for GITHUB library publishers to put the table description
into their README.md file as a (fp_lib_table) element where it can
be quickly copied to clipboard and pasted into the fp lib table dialog.
This is a paste operation, and overwrites from the initial cursor position.

Fix throwing of IO_ERROR in plugin.cpp by converting function name to wxString.GetData().
Switch to const PROPERTIES* in GITHUB PLUGIN functions.

Enhancement in Excellon file reader: accept Feed Rate and Spindle Speed definitions in Tool information line (but does not use them)
Eeschema: better name for m_SheetList (changed to m_SheetPath) member of class NETLIST_OBJECT.

Eeschema: better name for m_SheetList (changed to m_SheetPath) member of  class NETLIST_OBJECT.

Eeschema: netlist generation: fix bad choice for the "best net name" when selecting a net name between labels connected to the same net.
Code cleanup and remove unused file.

* Use wxAuiManager perspective to save and load window settings which should
  allow us to start using more advanced wxAui features like detachable tool
  bars and windows.
* Remove sash size change events, event handler, and sash width clamping code
  since it didn't work all that well anyway.
* Disable the close button on the footprint view pane.
* Update the footprint list box selection when iterating the list using the
  tool bar arrow buttons.
* Merge code from modview.cpp into modview_frame.cpp and remove modview.cpp.