Move all tap/session/event polling into SyncManager.

TapManager is no longer coupled to KegbotApi.
Add calibration activity.
Add OkHttp (built from git).
Add Request and Http, simplified helpers for making http requests.

Inspired by python-requests and/or rage at apache commons complexity.

Needs unit tests.
Move api implementation to Request + Http + OkHttp.
Delete httpcomponents.
Delete dead code.
Add calibration api.
FlowManager: don't activate on the focused tap if it's offline.
Implement new keg.
Kegboard: add paranoid bail-out.
SoundManager: reduce logging.
Add jsr305 to exported list; fix proguard.
BackgroundManager: allow reentrant open/close.
KegboardManager: add timeout while STOPPING.
Calibration: change hardware strategy.

Re-use an already running core to step around potential USB host issues.
SyncManager: break on interrupt.
BluetoothManager: synchronize around mQuit.
v1.0.0b37