* Move initial batch of shaders and presets to smoothing subdirectory
* Rename smoothing to edge enhancement
* Move cubic and windowed into interpolation
* Fix some presets
* Fix rest of presets
* Rename edge-enhancement to edge-smoothing
* Move pixel art scalers into separate directory separate from 'interpolation'
* Flatten interpolation/cubic into interpolation/
* make a bunch of implicit scaling rules explicit and move color shaders before scaling shaders in the handheld directory
* remove extraneous file
* switch vhs from viewport to source scaling
- Rename old catmull-rom-fast to catmull-rom;
- Add new catmull-rom-fast shader;
- Delete old b-spline-fast as it behaved exactly like bilinear;
- Add new b-spline-fast shaders;
- Add anti-ringing code to bicubic fast shaders.
