Graph Editor: Added operator to 'bake' keyframe-based F-Curves to be composed of...

Graph Editor: Added operator to 'bake' keyframe-based F-Curves to be composed of samples.

This operator can be activated using the 'Alt-C' hotkey for now, and operates on selected + editable F-Curves. This is currently still highly experimental, and does crash

I've implemented this as a way to test out the FPoints/samples code, which will be used to provide better support of the dense F-Curves which result from importing Mocap/BVH data. These should use considerably less memory + have a few additional benefits over keyframes when they're working in a stable fashion.