audience: deployers

level: patch

Added `__version__` and `__lbheartbeat__` endpoints to all services. Can be reached at `/api/<service name>/v1/{__version__, __lbheartbeat__}`.

These were added to comply with the [Dockerflow standard](https://github.com/mozilla-services/Dockerflow/#containerized-app-requirements).