Blender Git Loki

Don't use the refkey for calculating shape deltas, but only for the base
shape.

Shape keys distinguish between the base shape (shape without any keys)
and the individual reference shapes for each shape key (which define
the delta offsets). For strand shapes, which have to work on top of
animation, the base shape must be the original cache result rather than
a static shape, but the delta for each keyblock is still calculated
wrt. an explicit shape.