Substantial filter update

Update mostly related to filter, rewritten to fully support any color mode (L, LA, RGB, RGBA). Added wrap around processing for seamless textures and options for protect alpha/filter alpha channel.

Averager.py GUI rewritten to work with new filter features, more informate "Info" added, filtered/saved status shown to mimic Photoshop/Fireworks/Paint Shop Pro.

POVRayThread.py got minimal update to cope with new filter.