Wavetablesynth

Further optimization: increase the initial oversampling to 25x, but only do the additional linear interpolation on A1/B1 (because those are the oscs that get modulated and benefit most from the accuracy). By doing this I managed to cut CPU consumption to about half-one third. I feel this is the just about the best compromise between performance/quality here. Might increase the oversampling a bit more, will have to test and see if doing so brings any noticeable benefit.

Also, added two presets I made.