Blender Git Loki

Create sphere collision shapes for the hair point ghost objects.

NOTE: Bullet sphere collision shapes are created directly in the hair
code atm, bypassing the RBI API! This should be resolved eventually,
using the API everywhere instead of directly accessing Bullet. The
problem is that collision shapes in Bullet are an abstract base class,
the actual types are subclasses, which are difficult to handle nicely
in a C API ...