Mesh: Allow per-vertex material attributes
Mesh: Allow per-vertex material attributes

- Modify addMaterialLibrary to assign materials to the correct material
  index so makeBufferData can them it to generate per-vertex attributes
  out of the material values
- Add attribute cases to makeBufferData to allow for material attributes

frenchtoast747/webgl-obj-loader,frenchtoast747/webgl-obj-loader,frenchtoast747/webgl-obj-loader