New3dapi, various changes

- Add model ctor
- Generate ids for newmaterial if none given at construction
- Very basic modelbuilder class, just a placeholder for a better one for now
- Use bits for VertexAttributes#Usage (please check impact)
- Fix bullets tests, commented SoftMeshTest (going to rewrite)
The bullet test run now including lights. Will check the code for performance/readability when the new 3d api is final.