Model Editor: Transformations
- In `CafuModelT`, the joints hierarchy for the bind pose has ''absolute'' transforms, but the joints hierarchy for the anims has ''relative'' transforms -- both should be ''relative'' though: - eliminates inconsistency, - proper submodel rendering also in bind pose (no animations required in submodel), - transformations of the whole model (at the root joint) become much simpler and more reliable.
- All transformations (especially at the root joint, but elsewhere as well) should ask the user whether they should apply to the bind pose and all animations, or only a subset thereof (`wxGetSelectedChoices()`).
- A customizable, spatial grid like in the Map Editor should be provided.
- It's not 100% clear what our models default orientation is. Right now, "ahead/forward" is along the x-axis, which seems to be in accordance with many games (e.g. HL1 through Q4), but there are reports that HL2 uses "ahead/forward" along the y-axis, which I'd much prefer, as it's much more natural (TODO: check HL2 SKD?).
- Finally, it's not entirely clear to me what rules we should impose on the origin and bounding-boxes of models, if any. For example, should the origin be at the "bottom" of the model, so that placing it on ground is easier, or can it live at an arbitrary point that the artists choses, e.g. the center of the model?