KappaPT Preview P4 (Patreon)

This update has some interesting new features, although that comes at a slight performance cost (not as bad as P1 vs P2 tho).

- added partial spherical harmonics
- tweaked filter behaviour
- fixed black artifacts around sky areas of the screen
- adjustments to adaptive accumulation (still has some issues)
- minor sspt optimisations
- added user friendly settings names
- improved global illumination behaviour

Enjoy this bunch of additions :)