* Set default button on all dialogs that do not already have a defined
default button. The only exception is the EESchema net list dialog
which needs converted over to wxFormBuilder and due to it's design makes
setting the default button in any tab other than the default tab
problematic.
* Fix escape key dialog handling bug in EESchema print post script
dialog.
* Remove all occurrences if #ifdef USE_WX_ZOOM and all associated code within
the #else/#endif block ( old zoom code ).
* Removed the build option for USE_WX_ZOOM from CMakeList.txt and config.h.in.
* Removed all scaling code in base screen object.
* Fixed buffered paint and buffered client DC on Windows. Buffering works
properly on Linux and Windows.
* Modified kicad_device_context.h to automatically uses buffering on platforms
where double buffering is supported natively.
* Remove all of the scaled versions of the drawing functions in gr_basic.cpp
and any support code.
* Removed all traces of ActiveScreen global variable from eeschema and
gerbview.
* Renamed Recadre_Trace to RedrawScreen in draw frame object.
* Renamed PostDirtyRect to RefreshDrawingRect in draw panel object.
* Lots of code cleaning an Doxygen comment improvements.