Eq rack2

This is an updated version on Nicus EQ Rack Branch.
It enables the full power of the effect back-end for the EQ Knobs as well.

You can select which EQ should work on which deck and you can load any other effect to the EQ Slots.

Next steps to merge:
* Add a second Effect slot, to utilize the Filter knob / fourth band, some Controllers offer.
* Add an effect chain to preferences for master EQ 

  
We may add them in a separate Pull request. 
This PR focuses manly to use the Controller/GUI EQ knobs. 
Normally all other channels do not have such knobs, so we might implement it like the master EQ with gain sliders in the preference pane.