Texture atlas support

[Nathan Pointer]

Texture atlas are single files with multiple textures in them. This will be helpful if you are nearing the 16 texture per material limit or trying to reduce total number of files downloaded

[Nathan Pointer]

Detect if there are any duplicate textures

generate a maping reference

    [surface]: {
        normal: {
            physicalTexture: map*
            offset: [x,y]
            size: [x,y]
        }
    }

for duplicates, the offset and size will be unnessisary

in the shader create a :

• uTextures[16]
• uTextureMap[surfaces.length]
• uTextureOffset[surfaces.length]
• uTextureSize[surfaces.length]

[Nathan Pointer]

Instead of using atlases opted for the simpler TextureArrays built into webgl.

shipped with #30