* AnimInverseKinematics: debug draw for secondary targets
* AnimInverseKienmatics: better clean up of ik target debug draw
* GeometryUtil: added findPlaneFromPoints()
* ViveControllerManager: external dependency on eigen
* ViveControllerManager: record history of left/right hand controllers
* ViveControllerManager: use history to determine user shoulder location for better calibration
* ViveControllerManager: pass defaultToReferenceMat by const ref to calibrate functions.
* CMake: added external depenency to eigen linear algebra library.
* 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.
* Navigation walk speed has been reduced
* Tuned IdleToWalk timescale and interp time to reduce foot sliding
* Tuned fwd, back and lateral characteristicSpeeds to better match the
animations. This reduces foot sliding when moving forward and backward.
* Reduced rig state machine hysteresis to 1/60th of a second.
* idle is less masculine and works better on prescilla & art3mis avatars.
* idle to walk transition is updated to work with this new idle.
* turn in place animations are improved.
* fly animation is more symmetric.
Improves FTUE, by no longer going over the network to download default avatar animations.
This also includes support for relative animation urls within the animation.json
