The GL textures are now generated and updated as required, handled
and owned by the batch itself. This is the final bit of GL specific
code removed from display objects themselves, meaning that texture
instances can now be used in multiple renderer instances and it
paves the way for better handling of lost/restored context.
Added missing js file in the bunnybench example.
Destroying of textures now takes a bit more effort on the part
of the end developer - since those textures must be destroyed
explicitly by passing them to the renderer destroyTextures method.