CMake: add definition KICAD_TESTING_VERSION and KICAD_STABLE_VERSION.
One of these 2 options *must* be now defined (i.e. run cmake with option -DKICAD_STABLE_VERSION or -DKICAD_TESTING_VERSION
Stable and testing branches should be more easier to maintain.

fix an issue created by commit 2954. Gerbview: display now an indicator of layers in use. minor code cleanup.

* store selected language by name instead of wx language id (that changes between wxWidgets version)
* accept always comma and point as flotating point separator.

fix 2 minor bugs: GERBVIEW: Button "Erase all layers" not working, EESCHEMA: Plot to Clipboard: EDA_DRAW_FRAME::PrintPage() error

Pcbnew: dialog plot: make message window resizable, add tool tip and remove unused sizers.

Commit installer translation files for Japanese

Pcbnew, Module Editor: fix bug 707692 and other potential crashes (when having a block command in progress and try to make an edit command)

This was due to a duplicate constants ( with sligtly different values)  used to select items in some seach functions that broke filtering. Old definitions removed.

Pcbnew: fix that prevents loading modules from libraries (footprint name not identified in lib)
Module Editor: Try to fix incorrect printing. Fixed now only for scale 1. Nor working for other scales. (Work in progress).
Gerbview: Known bug: printing not working.
VRML export: Fix incorrect export of 3D shapes rotations when the 3D shape was rotated.

fixed others very minor bugs.

All: fixing a recent problem when using scroll bars: the full screen was redrawn, that can be very slow in Pcbnew.

Big cleanup of sourcetree root structure, added Documentation subfolder, moved packaging stuff for osx and windows (nsis) to packaging.