Blender Git Loki

Add some header info about asset errors or reload needs.

Again, rather rough UI but enough to be useful for now.

Add simple dummy code in outliner to show assets and their status.

This is purely WIP helper stuff, final UI will need real work - but that's for later.

Merge branch 'master' into asset-engine

Merge branch 'master' into id-remap

Merge branch 'master' into asset-engine

Conflicts:
source/blender/blenkernel/intern/blender.c
source/blender/windowmanager/intern/wm_files.c
source/blender/windowmanager/intern/wm_init_exit.c

Merge branch 'master' into id-remap

Actually hook async job of asset updating!

Add 'ensure_uuids' callback to API, fix some flags in RNA code.

Make opening .blend file use new async 'check asset updates' operator.

Nothing much exciting really, just not blocking anymore.

Merge branch 'master' into asset-engine

Conflicts:
source/blender/windowmanager/intern/wm_operators.c

Merge branch 'master' into id-remap

Conflicts:
source/blender/windowmanager/intern/wm_operators.c

Asset update: WIP proof-of-concept async (job-based) update code.

Builds, but not tested nor hoocked to anything yet!

Merge branch 'master' into asset-engine

Merge branch 'master' into id-remap

Move core of update check to BKE's asset area, add an operator for that too.

Merge branch 'master' into asset-engine

Merge branch 'master' into id-remap

Make 'check update' async, and add possibilities for engines to make async callbacks 'immediate'.

So now, jobs callback (async ones) of asset may return a specific job id value in case they actually
complete (or fail) on the first run.

This allows engines that do not need slow async stuff to perform an action to use simpler code
(e.g. imagine an engine able to list its assets from a cached DB, in most cases its list_dir
callback can execute instantaneously (from a user PoV), no need for a listing job then).

Make asset engine's `load_pre` callback mandatory now.

Reason is, even if paths returned by `list_dir` are OK, we will also use `load_pre`
during 'reload'/'update' scenarii, where we only have uuids, to retrieve final
.blend datablock paths.

Merge branch 'master' into asset-engine