Create a global registry to hold all the currently active Rig instances.
Use this registry and it's mutex to prevent accessing the rig after it has already been destroyed,
or is in the process of being destroyed on the main thread.
Make sure to explicitly set the _geometryToRigTransform in Rig::initJointStates().
This should fix small bounding volume when switching from the Gamebot avatar (which has 0.008 scaling)
to another avatar (which ususally have 0.01 scaling).
IK is no longer performed during capsule calculation, This fixes an issue with the mannequin avatar in the marketplace.
Specifically, it was causing the hips to rise during IK which would result in an incorrectly sized and offset capsule.
Also, A change in how the bone name to bone index lookup occurs exposed a bug
in Rig::computeAvatarBoundingCapsule(), basically it was not actually preforming IK,
and the ik targets were in the wrong coordinate frame. So when IK was actually
performed it would give bad results. This bug is now fixed.
* Added new anim node AnimDefaultPose
* AnimNodeLoader was changed to support the addition of the AnimDefaultPose node
* Edited default avatar-animation.json to insert an AnimOverlay and AnimDefaultPose between the IK node and the rest of the "underPose".
* Rig uses this to fade in default pose for the toes when the hip/feet puck are active.
This effectively deadens the toe animations, without effecting the hand animations.
* Also, the rig was changed to use the LimitCenter solution when the feet are enabled but the hips are not.
There are still some issues with rotations of the elbow pole vectors.
* When the (hand - shoulder) vector approaches the normal vector used in Rig::calculateElbowPoleVector() unexpected twists can occur.
* Also, when the (hand - shoulder) vector approaches zero, the IK system starts to flutter between two states.
* The shoulder twist constraint probably needs to be opened up for more natural range of motion.
* Bug fix for problem when chest target is enabled but hips target is not.
* centralized the two computeSplineFromTipAndBase functions into one.
* Removed dead code
