* Enhance class PLUGIN's comments to improve their value as instructional.
* Switch #includes from "file.h" to <file.h>, and fiddle with search paths
by using include_directories(BEFORE ...)
* dialog_page_settings did not have symmetrical space on its right border.
And it now remembers it last position and size within a program session.
* base_screen.cpp is now compiled twice, once for {pcbnew,cvpcb} and once
for eeschema, in preparation for "compile time" support of internal units
rather than "runtime" support.
* All header files used to create the PCB common library now compile as
stand alone code. This prevents the need to define them in a specific
order to make source code compile properly. It should also now be
possible to relocate the source code to build the common PCB library
to a separate folder.
* Fix grid select box update bug on context menu.
* Fix via size and track width select box update bugs.
* Fix layer pair indicator button update bug.
* Fix auto track width tool bar control enable bug.
* Fix via size and track width select status bug in context menu.
* Fix layer select box and layer control widget select bug when current
layer is removed.
* Add virtual function to notify objects derived from EDA_DRAW_FRAME that
the units setting has changed.
* Coding policy class naming fixes.
Lorenzo Marcantonio
jean-pierre charras
Dick Hollenbeck
Wayne Stambaugh