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)

> I just think probably using an anti-aliasing filter is unnecessary -
> there shouldn't be any extra >nyquist noise introduced by any of the
> filters, and anything introduced before the EQ has already aliased and
> thus can't be fixed by the EQ anyway...
> 
> On that note, I wonder if also the oversampling should be switchable
> (maybe even for each filter individually?) since in biquads, it's not
> always necessarily a desirable feature... in some cases, oversampling on
> biquads can actually be counterproductive (IIRC it can introduce more
> noise on low cutoffs, or something).

If there is not going to be a lp to remove aliasing, because there wont be any, is there anything gained by oversampling? 

 sorry this is where my knowledge of oversampling stops