XD-920 Update MQTT to Snapshot

Fix for Stopping the adapter when no broker
Update to Paho client
XD-906: Refactor aggregate counter resolution.

Create an enum for the package and use this in preference to Joda
DateTimeField. We don't need any of the latter's functionality
anymore and it can't be used for months or years.
XD-906: Add query by month to aggregate counter.

Also changed the test to run across more date boundaries
(e.g. 2013-2014) and fixed some bugs related to this.