Streams 211

Added the BroadcastMessagePersister interface which allows us to persist serialized JMX messages (like the ones we aggregate in the BroadcastMonitorThread). There is an implementation of that interface which persists those messages via a HTTP POST to a URI that is defined in the Streams configuration

This PR is dependent on https://github.com/apache/incubator-streams/pull/123 so once that is merged in, this PR will drop in size considerably.
Sure, I didn't know if we wanted to keep all pojos central to the same module. If that's not the case I'l move these over to the monitoring module