* Implemented Fallback to Bilinear controlled by user param.
* At its default value it gets rid of most ddt artifacts by falling back to relied bilinear filtering.
* At value 1.0, it behaves as original DDT shader.
* 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/