Search for the '_UV1', '_UV2' flags also in the names of the UV maps,
also check if the UV map used by the texture is valid.
Added support for exporting emissive textures, the emissive color will
be a shade of grey.
Added support for the AO technique with "_AMBIENTLIGHT" in the texture
slot name, instead of "_LIGHTMAP" which uses the LightMap technique.
Guide updated.