Blender Git Loki

Combined storage of render and realtime data in caches.

Caches now create 2 new roots below the main 'top' object of Alembic:
root and root_render for realtime and render data respectively.
This makes it easy to switch the whole archive to either of the modes
during baking and for constructing dupli caches.

Alternatively individual objects could store hires versions of their
data. This would also be more efficient if the cache contains many
simple objects which don't have 2 different variants. However, such
design decisions are difficult to make at this point and the
implementation can be modifier later.