crash bug on the phone side fixed (maybe)

Seems that when Android is trying to clean things up, it starts killing things left and right, and WatchCalendarService was blown away, generating a user-visible popup that it died, while other things killed at the same time died cleanly. Hypothesis: this is because the CalendarFetcher thread was still running. Added code to onDestroy() to kill that off.
reengineered phone side to work single-threaded like the wear side
bugs fixed, CalendarFetcher merged
less code is less
removed locks, cleaned up notes
release to beta