New effects and filters

I've added two new effects - "crush" which simulates bit quantization, and "coarse" which simulates resampling - and added highpass and bandpass filters.  The filters use new parameters "hcutoff", "hresonance", "bandf", and  "bandq".  The highpass is implemented as the remaining signal after a lowpass of the same type already in Dirt. The bandpass is a simple two-pole RLC.

To actually use these, you need a new version of Tidal (I've submitted a pull request for that one as well).  You can use previous versions of Tidal with this new version of Dirt.  The reverse is not true (new Tidal requires new Dirt).