Autopacking

[JJL772]

Support automatic packing of MRAO maps and height into normal. This is for compatibility with the PBR shader.

The following rules should be adhered to:

• ambient occlusion: _ao.xxx or _ambientocclusion.xxx
• metalness: _metal.xxx or _m.xxx
• roughness: _r.xxx or _roughness.xxx
• color: No postfix or _c.xxx or _color.xxx or _albedo.xxx
• height: _h.xxx or _height.xxx
• normal: _n.xxx or _normal.xxx

Each file in the directory needs to be processed. If the file matches any of the color map specification (_c, _color, no postfix or _albedo), then vtex2 will determine the "stem" file name. It will then figure out the other map components for packing.

The implementation should probably defer actual processing until it's actually read all of the directory's contents. Upon encountering the base name, it should create a new "texture set". Anything that matches an existing texture sets stem will then be added to the texture set. At the end of processing, all files will be packed.