Blender Git Loki

BKE: Add 'mesh remap' code.

This is the (big!) core of mesh transfer data, it defines a set of structures
to represent a mapping of mesh elements (verts, edges, polys of loops) between
two arbitrary meshes, and code to compute such mappings.

No similarity is required between source and destination meshes (though results
when using complete different meshes are rather unlikely to be useful!).

This code is not bound to data transfer, it is defined to be as generic as possible,
and easy to reuse or extend as needs arise.

Several methods of mapping generation are defined for each element type,
we probably will have to adjust that in future (remove useless ones, add
new ones...).

For loops, you can also define islands (for UVs e.g.) so that loops of a same
destination polygon do not 'spread' across several source islands.

Heavily reviewed and enhanced by Campbell, thanks a lot!