Blender Git Loki

New cache modifier type "Strands Key" for implementing shape keys on
cached strands data.

This modifier acts as a container for shape key data (i.e. as part of
the cache library). Such shape data can be applied to cached strands
data, which allows tweaking of animated hair shapes.

This could work both as a shape for the strand goals (adding dynamics
on top) or as a final modification after dynamics. Both methods have
their advantages (pre-sim allows control and sim at the same time,
post-sim gives accurate shapes but becomes rigid).