Blender Git Loki

Bugfix, report from studio Manos;

This tweaks the dependency rules for Scenes/Objects a bit. Here is the
rule:

- Each Scene has own dependency graph, and only solves dependencies for
objects in the scene

- However, when using multiple linked Scene-sets, the *current* scene is
allowed to have dependencies to objects in a 'set'.
This works by first calculating the sets, then the current scene.

Example: the current scene can have lights with a track/location
constraint to a character in a set.