Blender Git Loki

Use full transformation of B-Bone segments in Copy Transforms.

Currently constraints can only read the location along the
spline. This obviously limits opportunities for complex bone
interactions in rigs.

This patch exposes access to rotation and scale as well in
Copy Transforms. However, due to the way how things work,
this data cannot be smoothly interpolated, and abruptly
changes when switching to the next segment.

Reviewers: aligorith

Differential Revision: https://developer.blender.org/D3545