- went over every BM_SetIndex call and added comments about its use, if its setting dirty values or correct ones.
- replace loops over all elements _just_ to set index values, with a new function, BM_ElemIndex_Ensure(...), this will eventually only initialize values when they are dirty.
as does only edges and individual faces extrude (individual vert
extrude already did).
Note that I need to port this, after we all figure out how to handle
operators with variable transform follow-ons.
I also implemented the merge->collapse function, which is currently
accessable under ctrl->v, Bmesh Test Operator. I still need to
implement the other merge modes, and properly hook everything into
the merge menu tool, which I plan on doing soon (tomorrow hopefully).
The cool thing about the collapse tool, is not only does it handle (all)
UV layers, it handles vcols as well. To do this, I had to add a few math
functions to the customdata API, which seem to be working well.
