Ragdoll Part4: ragdoll shapes follow target joints, visible joints follow ragdoll shapes

If you enable this option in the menu:   Developer -->Avatar_Options-->Collide_As_Ragdoll  then the avatar's skeleton's collision shapes will self collide and the visible positions of the joints will try to follow the positions of the skeleton's shapes.

To see the shapes being used for collisions enable:  Developer-->Avatar_Options-->Skeleton_Collision_Shapes.
Note that JointState::mixVisibleRotationDelta() blends  _rotationInConstrainedFrame into the delta before applying it to the visible rotation.  This provides axial stability of visible joint rotation --> so that they don't twist up.