Blender Git Loki

Move index offset from parsing to Object creation

The only place where the information needed about how many vertices
have been occupied by other objects is `mloop->v` since `v` has to
be in the range from zero to total vertices _in a_ mesh.

All other indices (edge, UV, normal) work best when they're parsed
the way they're written and the corresponding data from the global
list is read directly.

So instead of modifying every index just to keep `mloop->v` happy,
use a `Map<int, int>` for storing vertex indices. This reduces chances
of error greatly and avoid "indices to indices to coordinates".

`Vector` would've been very slow it being unsorted & lookups being done
for _all_ `mloop`s. `Map` gives no drop in performance.

UV vertices from `Geometry` have been removed since `FaceCorner`s store
a direct index indexing into the Global list of UV coordinates.