Lifecycle (start/stop)

[dhmlau]

Based on discussion with @raymondfeng @kjdelisle

• need to have minimal lifecycle to ensure we have graceful startup and shutdown
  • e.g. database connection, other connectors that hold resources
  • we need to have a way to stop the connection
  • currently app.start only does it for REST server

[raymondfeng]

See #1845

[bajtos]

@raymondfeng now that your pull request #1928 has been landed, is there anything else we should work on as part of this epic?

[bajtos]

Closing as done by #1928.