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)

The name of the plugin should probably be "Equalizer", just "Eq" may not be clear enough for everyone (especially non-english speakers). Filenames or other internal names don't need to be changed, just this display name that is shown to the user...