Add Bluetooth backup channel support

[glenviewjeff]

As of about a week or so ago, the integration stopped being able to control (or see the status of) my dimmer switch. The Cync app works fine. I reauthenticated the integration with GE and still, no dice. The device and entity just show "became unavailable" in the logbook, but show (incorrectly) as "off" in the history.

[glenviewjeff]

Update: I connected the Cync switch to Google Home and the switch wouldn't respond from there either, though the Cync app worked fine. I called their support line, which was staffed by a refreshingly highly competent employee. Apparently the switch can lose WiFi connectivity and get into a state where it no longer tries to reconnect. There is a hidden "air gap" switch at the bottom that you slide out for 30 seconds, forcing a reboot. Apparently, there is a Bluetooth backup communications channel for the switch that lets the app continue to control the switch even if the WiFi link is down. It would be nice if someone could decode the Bluetooth API for HA.

[nschimme]

There might be something here to build upon and expand: https://github.com/unixpickle/cbyge

Issue of note: unixpickle/cbyge#8