Increase number of materials, per-face materials, fixups for 4.7

[ChronosWS]

Change material array index type to uint16 to allow more materials. Allow individual materials per-face. Minor fixups for compilation warnings/errors for 4.7. NOTE: To actually use per-face materials requires a shader which can synthesize correct UV coordinates for the vertical faces - by default the UV coordinates are mapped to the XY vertex coordinates.