Blender Git Loki

- added ModifierData flag, is modifier enabled in editmode
- added modifier type flag: should modifier be enabled by default for
active in editmode
- added subsurf "debug incremental" option instead of G.rt==52 (it becomes
a slightly useful feature now for debugging how well a modifier works
with incremental subsurf... maybe important for future python modifier
developers)
- shuffled modifier button layout just to keep people guessing
- switched back to drawing editmesh face centers not through derivedmesh,
I didn't think this one through, forgot that centers were also used for
selection. have to think about what to do about this, should be either
(a) don't draw centers with a cage active (optimal mode) or (b) come up
with api to draw centers through derivedmesh and also handle selection.
- changed recalc_editnormals to also follow the len(no)==0.0 use vertex
co convention