Add softkey function to toggle inserted FX IN/OUT

In order to turn an inserted FX on and off we need a new option in the soft key function drop down. Suggestion is to call it ”FX In/Out” which would be consistent with others like ”Comp In/Out, EQ In/Out” etc. When selected, the Channel drop-down would list FX1, FX2, FX3, FX4.

This would solve the issue with Soft key mute FX(n) does not work on inserted FX - #6 by Vedeja