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)

> After some further testing... I think maybe we should reconsider using
> the LR4 filter in the Eq. Or at least make it optional...

The most tweaked parameter is the cutoff frequency, you could be right, or ....
I know the implementation was not correct, but it sounded and worked much better 2 bug fixes ago(iirc a missing - ). The roll off to the -6db was much tighter, and i was able to stack 4 of them. IMHO this is when the eq sounded it's best.

@diizy I would welcome your thoughts on this.