Reinstate crashlytics.

Only enabled for release builds. API key (not checked in)
is located in kegtab/crashlytics.properties.
Update and move protos.
Bump OkHttp dependency.
FlowToggle support.
KegboardManager: controller handling updates.

- Don't treat missing serial number as fatal.
- Mark conflict if a board with the same name already
  exists (required by previous).
- Attempt to set randomized serial number for boards
  that don't have them (i.e. DIY arduinos).
- Inactive controllers are added to the controller set
  so that they are reported in dumps.
- Flow toggle handling improvements.
v1.0.0-b65
api: Add more exception types.
api: Add getVersion support.
api: Add device link methods.
Refactor setup wizard; add device pairing support.
Activate on all taps, not just focused one.

Issue #78.
Exception updates.
v1.0.0-b67
AuthenticatingActivity: Grab core later.