Differing .bvh and deepMimic skeletons cause incorrect animation transfer

[sloganking]

Describe the bug
The deepMimic humanoid skeleton is quite simple. Due to this, many .bvh files may contain humanoid skeletons with more bones than the deepMimic humanoid skeleton contains. This is not a problem for extremities like fingers, as we can choose to simply not transfer the animations for extremities. However a .bvh skeleton with animated bones between what we designate as bones who's rotations should be transferred to the deepMimic humanoid animations, will cause the global rotations of deepMimic animations to be off, even though we successfully translate the local joint rotations.

Example:
A .bvh skeleton that has three spinal bones, hips, chest and upper chest. All of which are told to roll right 10 degrees. If we bind the deepMimic humanoid's hip rotation to the .bvh's hips, and the deepMimic humanoid's chest to the .bvh's upper chest, the .bvh's chest rotations will go uncounted for and cause the global rotation of the deepMimic's chest bone to differ from the global rotation of the .bvh's upper chest bone.

Expected behavior
To account for bones in .bvh files which the deepMimic humanoid does not contain. It may be desirable to transfer the global rotation (a bone's rotation relative to the world space or the model's root) of bound joints instead of their local rotations (a bone's rotation relative to its parent bone).

Additional context
This issue may want to be considered a stretch goal. One which can be worked on after we successfully achieve local joint rotation transfer