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.

release/scripts/modules/bl_i18n_utils/utils_spell_check.py

@@ -589,7 +589,6 @@ class SpellChecker:
         "yuv", "yuva",
 
         # Blender acronyms
-        "bge",
         "bli",
         "bpy",
         "bvh",