Blender Git Loki

Added the major parameters for the hair simulation.

This is basically copied from existing cloth sim settings, with a good
deal of cleanup and sanitization.

Unlike cloth parameters, the damping values are described as relative
to their associated stiffness values for springs. This is much easier
to use in practice and less prone to lead to unstable simulations.
Damping simply works best when the force is in the same order of
magnitude as the stiffness, so having a relative factor requires much
less adjustment on the user side.