Blender Git Loki

Relax Brush: Initial implementation

Work in progress. This still has a lot of bugs and I'm not sure if this
approach is the best for this kind of smoothing. The current
implementation can't handle poles with 5 vertices or more, so it doesn't
work properly with the result of the voxel remesher. It does not support
multires.
Also, I'm using gsets to store the smoothing groups. I'm sure that there
is a better way to do it. If for some reason someone enters sculpt mode
and touches a pole with 30 vertices it should not crash, but it adds an
unnecessary overhead when working with properly constructed quad meshes.