Blender Git Loki

bmesh python api change in internal behavior.

* Only have 1 python object per bmesh, vertex, edge, loop, face.
* Store pointers back to the python data in a custom data layer so as not to use more memory for normal editing operations (when pythons not running).
* Currently this data is created and freed along with the BMesh PyObject.
* Incidentally - this fixes comparisons for bmesh elements which wasnt working before.