Blender Git Loki

Fix collision distance calculation (makes collisions perfectly inelastic)

Collision distance was computed with respect to the positions before the
pre-collision solve, but should rather be computed with respect to the
newly solved positions.

This fixes the issue of the collisions being semi-elastic (bouncy),
making them pretty much perfectly inelastic. This also improves the
effectiveness of the collision response, preventing penetrations even
with far less collision steps.