ModelData is still allowed to load skins with more joints, since
the limitation is in the graphics side of things (Model).
Eventually we will use a buffer for joints to alleviate this.
Nodes can have either a transform matrix, or decomposed transform
properties, but never both. Using a union means we can store both
of those variants in the same piece of memory, using the existing
matrix boolean to figure out which one to use.
This reduces the size of the struct by 48 bytes (152 -> 104), which
ends up speeding up some model operations, I'm guessing due to the
CPU cache.
- Ref struct only stores refcount now and is more general.
- Proxy stores a hash of its type name instead of an enum.
- Variants store additional information instead of using a vtable.
- Remove the concept of superclasses from the API.
- Clean up some miscellaneous includes.