Filter speedup, GUI tuneup

Most important reason for current release is yet another filter speedup (ca. 7%).

Apparently GUIs for both main programs are updated to fix last minor issues that annoyed me from time to time.

Top secret future plans include fully reworking "Averager" GUI to modular for better screen space usage, therefore current release is likely to be the last one having stable and refined "classic" single window GUI. Grab it while you still have a chance!