Get face set create operator working for dyntopo

Merge branch 'master' into temp_bmesh_multires

* Added new paint API method paint_stroke_apply_subspacing, for various
things that need custom spacing (that is coaser than the brush radius),
and refactored the existing dyntopo spacing code to use it.

* Added option to topology rake to ignore brush falloff settings
(it forcibly uses Smooth falloff).

* Smooth and topology rake support custom spacing now.
+ This is especially important for the clay brush, which works
better at smaller spacings and with a bit of autosmoothing.
Now you can tell it to override the smooth spacing to be coarser,
leading to much better performance.

* Topology rake now has a projection setting similar to autosmooth
which defaults to 1.0 (to preserve current behavior).

The main motivation for this commit was to make topology rake work
better for normal brushes. This is now possible, however it tends to
make the brush slower and also the settings are a bit fiddly.
We might want to make dedicated brush presets for this.

Btw, the UI for brush settings are becoming a real mess. Help!

* Added a "projection" option to smooth/autosmooth. It works by
projection neighboring vertices onto the current smooth vert's normal
plane, multiplied by a "projection" factor. This is extremely similar
to what the surface laplacian produces, but is much simpler, uses
no temporary state and thus can be used in more places.

Merge branch 'master' into temp_bmesh_multires

Also fixed a pose brush bug that may or may not have been
the result of the merge nixing code, need to check master.

Fix a few cast warnings

Fix invalid parameter type in bmlog.

* Eeek, left in an ATTR_NO_OPT attribute

* The dyntopo remesher is now a bit smarter about avoiding
certain degenerate cases that produce lots of bad geometry (and
also bad PBVHs that slows down the whole mesh).
+ A very small amount of surface smoothing is now applied by dyntopo.
+ The recursive functions that expand the region considered by dyntopo
now ignore "front face only" for depths less then 5.
+ The number of edges dyntopo can split or collapse in one run has been cut in
half to 4k.
- This limit is also now dynamically adjusted by a measure
of how skinny the edges are.

fix compile error

Fix last commit flipping the order of booleans.

* Got box trim tool working for dyntopo
- This required implementing SCULPT_UNDO_GEOMETRY for dyntopo.
That turned out to be more work then I expected. Basically
it writes an entire Mesh to BMLogEntry, which can be swapped
with current bmesh. Tricky part was patching bm log ids.

Edit face set brush now works for pbvh bmesh

Enable color filter brush for pbvh bmesh

One more null ptr check

* Fix null ptr bug in automasking code

* Fix bug in last commit where boundary flags weren't properly
updated after symmetrize.

Fix memory corruption in sculpt neighbors code

* Boundary info is no longer initialized with
SCULPT_boundary_info_ensure, instead PBVH_BMESH keeps
track of boundary vert flags internally. This prevents
nasty first-click lag on the smooth brush as well as anything
with autosmooth.

* Fixed SCULPT_dynamic_topology_sync_layers to properly sync
active/render/clone/mask layers indices.
* Fixed sculpt color bugs in pbvh drawing for bmesh.