Added effects and filters

These *require* the new version of Dirt, see the pull request there for some the source on how they work.  In summary, there are new parameters: crush, coarse, hcutoff, hresonance, bandf, bandq.

Crush simulates quantization to a specified bit depth, coarse simulates resampling by every Nth sample, and the other parameters are for highpass and bandpass filters.