Blender Git Loki

Preliminary fix for bad level calls to WM job functions from BKE.

The job invocation should happen only in editors/. Also it makes sense
to modify the bake operator such that it supports both the basic cache
library and an optional modifier output.

The design for this area is in progress anyway, probably the cache
library archive paths will be changed so that there is always one input
and optionally an output path, with all the modifiers working in
sequence.