Cycles Baking, early commit

I squashed the previous commit to undo the rename of bake.c > bake_old.c
This was merge-conflict prone since any change in the bake.c would generate conflict.

(same for object_bake.c)

* More work on getting cycles to have its bake function called.
* Getting through the beast - bake gets called inside Cycles
* I get a crash though, on free_session()
* Get render pass for baking from enum
* Sending the BakePixel and float pointers all the way to Cycles \o/
* Sending some data back just to validate the pipeline going in and out