Rename User Function button names.

Add capability to rename the User Function button mute group names. Presently, these are something like Mute Group 1, Mute Group 2. These names can be changed locally in the UC Surface software, but not transferable to the hardware. It would be nice to assign names at the mixer, e.g., vocal mute, band mute etc.

Along with that, why weren't the User Function button scribble strips electronic? Doh!