Graphic EQ Effect

Thiss PR adds a 10 band static equalizer based on Biquad filters. The implementation of the Biquad filter is based on @daschuer's iireqs branch.
As we have recently learned, this not a fixed count of frames. 
According to fiview, it took 132 Samples to pass a BpBq/2/1000
Since killing an entire band is no common use case for this graphic EQ, I think we could always process it. 

Otherwise you may utilize the new filter start from: 
https://github.com/badescunicu/mixxx/commit/2c4931471c791127b5c034a2e3dbb296417ebf0e
by initalize it again with setCoefs()