Blender Git Loki

Better sorting when we are displaying several levels at once, for 'lib' append/link.

Consider blendfiles and 'categories' inside them as regular dirs, but with this hierachy:
real dir > blende file lib > category in a blend lib.

This gives a much better sorting (among other things, gives more importance to
blend files!).

Merge branch 'master' into asset-experiments

Conflicts:
source/blender/blenloader/intern/readfile.c
source/blender/editors/space_file/file_draw.c
source/blender/editors/space_file/file_ops.c
source/blender/editors/space_file/filelist.c

Merge branch 'master' into asset-experiments

Reworked from scratch 'icon over previews' feature.

Previous implementation was horribly complicated in the end... sigh.

Fix crasher (Looks like PointerRNA->type can be NULL...).

Merge branch 'master' into asset-experiments

Merge branch 'master' into asset-experiments

Merge branch 'master' into asset-experiments

Merge branch 'master' into asset-experiments

Fix for Windows - 'foobar.blend' is a valid file path to that OS, sigh...

Also, store temp nullified pathsep in chars now, better.

Fix stupid UI/py bug after recent refactor.

Merge branch 'master' into asset-experiments

Merge branch 'master' into asset-experiments

Merge branch 'master' into asset-experiments

Merge branch 'master' into asset-experiments

Conflicts:
release/scripts/startup/bl_ui/space_filebrowser.py

Recursive listdir: let user set level of recursion...

Merge branch 'master' into asset-experiments

Merge branch 'master' into asset-experiments

Merge branch 'master' into asset-experiments

Reorganization:
* Make 'clear preview' a C operator;
* Move 'object preview generator' op in wm namespace;
* Add those two to file-> data preview submenu.