Refactor pi-dial to use Python's async / await

[prcutler]

Python's async and await need to be added to pi-dial which will require a rewrite.

1. The denonavr project uses async and it's the correct way to call functions for the receiver. I'm currently using legacy functionality that may be deprecated in the feature.

2. Using async will also allow new functionality: When muted, I can add a sleep method that turns off mute after a set period of time so I can be reminded if my needle is still going round & round on the turntable. Doing it now does not allow it to be unmuted until the sleep time has ended.