Blender Git Loki

Constraints: add support for a new Owner Local Space for targets.

Add a new transformation space choice for bone constraints, which
represent the local transformation of the bone in the constraint
owner's local space.

The use case for this is transferring the local (i.e. excluding the
effect of parents) transformation of one bone to another one, while
ignoring the difference between their rest pose orientations.

Owner Local Space replaces the following setup:

* A `child` bone of the `target`, rotated the same as `owner` in rest pose.
* A `sibling` bone of the `target`, positioned same as `child` in rest
pose and using Copy Transforms in World Space from `child`.
* The `owner` bone constraint uses Local Space of `sibling`.

(This analogy applies provided both bones use Local Location)

Since the space list is getting long, this adds a couple of separators.

Differential Revision: https://developer.blender.org/D9493

Merge branch 'master' into sculpt-dev

Merge branch 'master' into cycles_procedural_api

Merge branch 'master' into greasepencil-object

Merge branch 'master' into temp-gpencil-interpolate

GPencil: Show set operator only if selected is enabled

Merge remote-tracking branch 'origin/master' into temp_bmesh_multires

Also redid vcol boundary tool icon, and made a little icon for sculpt
color paint.

Merge branch 'master' into cycles_texture_cache

Merge branch 'lanpr-under-gp' into temp-lineart-contained

Merge remote-tracking branch 'origin/master' into lanpr-under-gp

Merge branch 'lanpr-under-gp' into temp-lineart-contained

LineArt: Proper Use of BMesh operator to remove doubles.

Merge branch 'master' into temp-gpencil-interpolate

Merge branch 'master' into sculpt-dev

Merge branch 'master' into sculpt-dev

Sculpt: Improve boundary artifacts in fairing mask with line gestures

Merge branch 'master' into sculpt-dev

GPencil: New interpolation set operator

GPencil: Interpolate Sequences with Hash tablet

Interpolate using the pair hash table and allow multiple interpolations.

GPencil: Allow multiple interpolations on same frame