Blender Git Loki

Mesh overrides for duplis from cached Alembic data.

If a duplicator has cached data it will now replace the derivedFinal
mesh of objects with the cached version for drawing.

This is a compromise atm: It would be better to actually draw derived
meshes directly, so that we don't have to modify objects. Then we could
also have multiple different instances of the same orignal object
(in whatever way these might be defined). DNA Objects would then be
totally separate from duplis, but at this point the drawing and render
code makes this unfeasible.