Blender Git Loki

New cache modifier type for creating force fields on duplis of the
cached group itself.

This allows using the dupli group objects themselves as force fields,
in particular for collision objects in strand simulation. Without this
feature only the original objects of are recognized by the effectors
system, and even if duplis worked properly their settings would not be
accessible due to linking and dupli group hiding. The cache modifier
circumvents this issue by providing a new force field system, separate
from the current effectors.