Alarm Clock, Shuffle, Repeat, and Crossfade

We added the following features and bug fixes:
- Added support for the Alarm Clock feature.
- Added support for shuffle, repeat, and crossfade.
- Added command line support for the alarm clock, shuffle, repeat, and crossfade features.
- Added and verified hardware support for the ZP120 hardware unit.
- Fixed a bug we encountered in how the group master node was set.
- Added an attribute to each speaker linking back to it's group_master. This allows slave nodes to relay commands to the group master node and eliminates bug where commands to slave nodes in a group return an error.