Blender Git Loki

Interpolation code for reading Alembic cache samples on subframes.

This features is needed for motion blur. All properties with position
semantics (transform matrices, mesh and curve vertex locations, etc.)
need to be interpolated for fractions of full frames, in order to
reproduce the motion and deformation correctly.

Alternatively we could store subframe time sampling for this subset of
properties. However, this would increase the amount of data stored,
and it might actually show artifacts from subframe interpolation in
Blender which is not visible to animators otherwise and should be
ignored.