Blender Git Loki

Apply all object collisions simultaneously

This makes all multi-object collisions be solved simultaneously, as not
to give any of them priority over the others (as in the sequential
collision solve that was implemented)

Note that self collisions have not been integrated, and are instead
solved independently after the object collisions. This is so that they
don't have to fight against the object collisions, as those are
generally more robust, and might cause issues with the self collisions.