Add query metrics.

-Metrics are optional (default off), and an example balboa configuration is commented-out in reference.conf
-Only balboa is currently allowed as a metric provider, but this is easy to change down the road

It is designed such that if ActiveMQ becomes unreachable, Soda Fountain will keep working (it will whine of course); in this iteration, it simply drops metrics. It attempts to reconnect to ActiveMQ using failover transport.

There are some unit tests around which metrics get recorded; I am relatively new to Scalamock but I think I did it right.

Once I get a "Ship It!" I will merge it into master and bump the balboa-client and balboa-common dependencies to 0.2.0 (instead of SNAPSHOTS).