Add basic IK system using quaternion pointing
Factored out CalculateSpaces()
Create, and use, smaller calculate function
Properly apply rot diff
Convert IK Angles to Euler and Back
Load, and enforce, IK angle limits
Load IK data for PMD files too
Make sure to sync all bones attached to IK-affected bones
Iterate on each chain, not on all chains
Direct-calc of 1/2-bone IK chains, based on reach and direction
Basic external bone effector support
Handle fully-inverted external effectors