Blender Git Loki

Merge branch 'master' into asset-engine

Kinda painful merge thanks to extensive changes to things like Main
listbases names, linking code, etc.

Conflicts:
source/blender/blenkernel/BKE_library.h
source/blender/blenloader/BLO_readfile.h
source/blender/blenloader/intern/readfile.c
source/blender/blenloader/intern/writefile.c
source/blender/makesdna/DNA_space_types.h
source/blender/windowmanager/intern/wm_files_link.c