* 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/
- Add CUT shaders. A kind of DDT shaders with some useful params to control interpolation;
- Fix DDT shaders (broken when porting from Cg to Slang). Courtesy of guest.r