split SkeletonModel and Ragdoll classes apart
cleanup Ragdoll API (less "ragdoll" qualifiers)
more correct names for ContactPoint API

renamed (and disabled) the useless enforce() to applyFriction()
changed the buildConstraints() method to more correct name: enforce()
will eventually change how ContactPoint actually works, but later
removed hackery from ContactPoint enforcement
no NULL check on delete SkeletonModel::_ragdoll
Merge pull request #3285 from AndrewMeadows/ragdoll

Cleanup of Ragdoll API