FBXLoader: Simplify animation system and support unbaked animations

[looeee]

The previous animation parser in the FBXLoader has a number of problems:

• It creates a flattened array with all loaded and adding them manually to the exported Group as Group.skeleton.bones. This was then used to animate objects - so a scene with a single rotated box would have a keyframe track references .bones[ box001 ].quaternion

• Only baked animations exported at one keyframe per frame are supported

• Objects animated on a single axis that is not the x axis won't work - times are specified separately per axis animated axis in FBX files and the x axis times are being used to create time values for other axes

This is a simplification of the system that addresses these issues and additionally:

• use the times directly from the FBX file instead of recalculating them frame by frame (this means that frame rate is automatic)

[mrdoob]

Sweet!

[mrdoob]

Thanks!