Pcbnew: fix bug #1272714 . Code cleanup: use 2 different enums for pad shapes and pad drill shapes. Remove never used pad shape.

move ${Boost_LIBRARIES} into cvpcb, pcbnew, _pcbnew and out of github, because worker threads used regardless of github

   To use multiple working threads.  This entailed adding KiCad typedefs:
*) Add typedefs for MUTEX and MUTLOCK which mask the actual choices for the project.
*) Add FOOTPRINT_LIST::DisplayErrors( wxWindow* ) which is a single strategy for
   showing aggregated load errors.  Although what's there is only scaffolding
   and needs a volunteer who knows HTML pretty well.
*) Ensure all callers of ReadFootprintFiles() use the new DisplayErrors() function.   
*) Push utf8.cpp and utf8.h into common library for open use.

* Make the tool bar dockable.
* Enable the overflow control in the tool bar in case the it does not fit in
  it's parent window.
* Fix some wxAuiPaneInfo usage issues.
* Remove unused wxAuiPaneInfo objects.
* Move perspective saving and loading into EDA_BASE_FRAME object in preparation
  for extending this to all frame windows.

Plot functions: some enhancements in mirror mode (Pcbnew specific): boards are mirrored horizontally, and the page layout is no more mirrored, and therefore is always readable.

Moved scaling of font glyphs to the moment when they are created (eliminated a few multiplications unnecessary variables).
Changed some magic numbers into constants.

Fixed SetCurrentContext() assert, that was firing on closure of pcbnew, when the OpenGL backend was active.

* Replace illegal file system characters when reading legacy libraries to
  prevent FPID parsing errors and allow saving to PRETTY file format.
* Create validator to filter illegal file system characters from footprint
  name text edit controls to prevent issues when saving to PRETTY file format.
* Add missing source file licenses and some minor coding policy fixes.

Now footprints, after loaded by reading a netlist are grouped by sheets by the footprints spread function, and the grouping is better.
Rename 2 files. Fix minor issues. Clean code

   comment for GITHUB_PLUGIN which should flow into Doxygen output.
*) Rewrote: 
        PCB_BASE_FRAME::Save_Module_In_Library(): now uses fp-lib-table and PROPERTIES.  
        PCB_EDIT_FRAME::ArchiveModulesOnBoard(): now can archive to any writable library type.
        PCB_BASE_FRAME::SelectLibrary(): is now generic for selecting a library, not just the active library.

Pcbnew: Code cleaning and bug fix in autoplace functions
Dialog exchange footprints has now a separate button to update the .cmp file, only on request.

Pcbnew: Fix a crash on exit when an item was previously deleted. Fix not working footprint exchange functions