Pour activity: don't re-use fragments; make FragmentStatePagerAdapter do it.
Make all internal events implement Event.

Also adds a few new event types (not yet used).
SoundManager: refactor; use SyncManager for event updates.
Http: log response code.
Pour activity: use internal events to update tap status.
Calibration: don't use obsolete rawMeterName.

Closes #32.
Calibration: toggle relay if present.

Closes #39.