Removing Blender Game Engine from Blender 2.8

Folders removed entirely:
* //extern/recastnavigation
* //intern/decklink
* //intern/moto
* //source/blender/editors/space_logic
* //source/blenderplayer
* //source/gameengine

This includes DNA data and any reference to the BGE code in Blender itself.
We are bumping the subversion.

Pending tasks:
* Tile/clamp code in image editor draw code.
* Viewport drawing code (so much of this will go away because of BI removal
  that we can wait until then to remove this.

source/CMakeLists.txt

@@ -29,7 +29,3 @@ endif()
 
 add_subdirectory(blender)
 
-if(WITH_GAMEENGINE)
-	add_subdirectory(gameengine)
-endif()
-