Remove comms display in hud

Removes the comms display in the hud for now, and adds structure for it to be re-added when VO is in. @BrettASwift @kadst43 
I wouldn't push this off on the trigger system - it's something that we want to have always happen, in a particular way, not something that the designer is going to want to customize per scenario, so it should be done in code.

The natural place to put it is probably in marsGameSound, which is the game-specific instance of the sound manager.  We need a couple other changes there first, though.