More edge tweaking.
* Expand max blur radius.
* Remove halfSize from Texture.
* Creation of renderbuffers at an exact size.
* Revert change that put texel space around the edges atlases.
Downscale optimization (remove one texture copy)
Image filters now only work on single-tile images.
* This allows for future optimization.
* Blur filter on multi-tile images did not work correctly anyway.
Texture filter can return a downscaled texture (upscaled when blended)