* Break out debug screen to a separate class and make it thread-safe.
* Break out power state to a separate class.
* Show battery voltage, charging & USB status on debug screen.
* Show GPS lock / no lock
* Fix an off-by-one that I introduced earlier in `drawRows`.
Work towards separating out how Screen interacts with other stuff.
* `Screen` should now be thread-safe. All commands to it are put in a
queue and handled in `doTask` from the `loop()` task.
* Break dependency from `BluetoothUtil` to `Screen` by changing the
pairing request into a callback.
* All accesses to screen now happen through the class.
* Fix `drawRows` so that the text scrolls along with frame animations.
* Remove example code that wasn't used.
The problem was we were pulsing the display power briefly down while
reentering the ON state (because the ON states exit rule turned it off).
Instead we now just turn off the screen on entry to DARK or LS states
* Suppress warnings about conflicting library names in platformio.ini by
explicitly picking the libraries by id that we want.
* fix unused static function warning by making it not static ;)
* declare arduino-fsm as dependency for BluetoothOTA. Hopefully this
fixes the CI builds?
Tested: `pio run` builds.
geeksville