It works on only one layer and one mip, and assumes the provided texture
data is compatible with the image, but does support sub-image updates
(x, y location as parameters, width and height in the texture data).
BSP textures are now two-layered with the albedo and emission in the two
layers rather than two separate images. While this does increase memory
usage for the textures themselves (most do not have fullbright pixels),
it cuts down on image and image view handles (and shader resources).
Loading is broken for multi-file image sets due to the way images are
loaded (this needs some thought for making it effecient), but the
Blender environment map loading works.
It optionally generates mipmaps, and supports the main texture types
(especially for texture packs), including palettes, but is otherwise
rather unsophisticated code. Needs a lot of work, but testing first.
