largely cleanups, though does include glCopyImageSubData for gl revs that support it
TODOS:
1) non glCopyImageSubData for `void GFXGLCubemapArray::copyTo(GFXCubemapArray *pDstCubemap)`
2) while we don't get corruption showing in >0 mips for irradiance maps using the newer code, it nevertheless renders wrong.
not 100% sure if renderdoc is showing blank mips because it expects it due to size, or if we are in fact generating em even though we don't use em in the end for irradiance references.
2) fed glTexSubImage3D GL_RGBA instead of a second GFXGLTextureType[mFormat]. this tells it what order colors come in, not what size
3)for safeties sake, skipped out on updatetexture if the fed cubemap isn't initialized yet
Got the initialization of the arrays to work, but currently fill the supplied cubemaps with flat 1 values(effectively filling with garbage) as sampling from the cubemap to feed to the array leads to memory/heap corruption.
