Blender Git Loki

Sculpt: Add extra deform types to Smear

The smear brush was using the stroke direction to slide colors across
the mesh surface (this is called drag in other sculpt tools). Similarly,
other deformations can be included. The most common ones in image
editing are pinch and expand, which can be used to sharpen transitions
between colors.

Reviewed By: sergey

Differential Revision: https://developer.blender.org/D8270