Even More Skinning...

This changeset does even more to improve skinning

- Deswizzle the weight format in plVertCoder, eliminates a loop and some float operations in the skinning code
- Replace code de-duplication macros with a clever template solution. This unfortunately removes support for skinning those "localUVWChans" that we've never seen in any of the game data.
- Slightly reduce the amount of data copying per frame
- Implement an SSE 4.1 skinning function

Things I didn't test: that the 3ds Max exporter still works.