Blender Git Loki

Bring back impulse scaled repulses

It seems I was a bit too optimistic in thinking that just distance based
repulses could handle contacts nicely. Turns out impulse scaled repulses
really have enough of an influence in making the collision response more
effective, that it is worth keeping it for now, even if at the cost of a
very slight stability reduction and and a bit of an increase in
collision elasticity.

I hope to come up with a better solution, and elliminate this, after
cluster based impulse pruning is implemented.