Eq plugin

Initial pull request for the native EQ plugin, #1376 

![image](https://cloud.githubusercontent.com/assets/7412852/5425560/4ecbfbbc-8314-11e4-9a7e-334e7910f87e.png)

why are you calling the setFrequency and setQ calls every period? That's a huge CPU sink right there... You should only call them when changed. Use the isValueChanged() function to your benefit here!

Also since in biquad filters, frquency and Q are interdependent (you have to recalc the coeffs when either of them changes) you should probably consolidate setFreq and setQ into one function (setFreqAndQ or something) because there's no benefit in setting them separately.