Adds basic glTF import (although right now it only imports back
positions) and fixes support for more of the vertex data that's
available to us. The MDL file isn't written back out yet either, it only
displays in the viewport.
Physis gained skeleton and deform file read support, so we can use that
and extract these directly from the game (without help of the Havok SDK
like TexTools.) The racial deform is still slightly off, but this is
still a pretty big milestone.
Instead of extracting item sheets one at a time, it's now done on
multiple threads. Loading gear is now faster since reused files are
cached, switching between races is still wasteful, but it's a good
enough improvement for now.
These parts (inspired by the KDE parts system) will allow the tooling
to reuse GUI mechanisms. Right now the two supported parts are for Excel
and Models, and exdviewer and mdlviewer will be retrofitted to them in
future commits.
