Blender Git Loki

'Transfer DataLayout' operator (WIP).

Functionnal, but not complete yet. Should be mostly usable though from modifier.

Notes:
* The logic of current 'transferdata' pre-process on data layout is reused here,
avoids duplicating code and ensure consistency in behavior, and does not add
*too* much complexity.
* Also fixed some issues and mistakes in that part that were affecting
TransferData feature itself too. Will need at least one more review pass,
though, this is complex logical code.
* VGroup: The 'delete' part is not yet implemented (option of plain operator,
to get an exact same data layout as source).
Need to first transfer some vgroup stuff from ED to BKE (esp. delete logic),
will do that in master as separate patch.
* Standalone part of the op is empty right now (but this should be mostly monkey coding).