This stores loop indices into the loop array giving easier acess
to data such as vertex-colors and UV's,
removing the need to store an MFace duplicate of custom-data.
This doesn't yet move all internal code from MFace to LoopTri just yet.
Only applies to:
- opengl drawing
- sculpting (pbvh)
- vertex/weight paint
Thanks to @psy-fi for review, fixes and improvements to drawing!
595a491e63