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/startup/bl_ui/properties_data_bone.py

@@ -433,7 +433,7 @@ class BONE_PT_deform(BoneButtonsPanel, Panel):
 
 
 class BONE_PT_custom_props(BoneButtonsPanel, PropertyPanel, Panel):
-    COMPAT_ENGINES = {'BLENDER_RENDER', 'BLENDER_GAME', 'BLENDER_CLAY', 'BLENDER_EEVEE'}
+    COMPAT_ENGINES = {'BLENDER_RENDER', 'BLENDER_CLAY', 'BLENDER_EEVEE'}
     _property_type = bpy.types.Bone, bpy.types.EditBone, bpy.types.PoseBone
 
     @property