Initial work on a mockConnector that simulates a (very badly simple) XMPP server (#18)

This version of the mockConnector uses an hash map address -> connection to route packets from one connection to the other.
Added gauges to queue depth in incoming and outgoing dispatchers (Issue #17)
Api improvements towards improved ability to meter

- dispatcher receives incoming packets directly from Connector
- connectors nut be registered and are assigned a unique ConnectorId
- moved the abstract parts of Connector to a separate package (to become a separate project)
Implemented per-connector incoming packet counter (Issue #17)
Merge branch 'snapshot' of github.com:mcaprari/botto into snapshot

Conflicts:
	botto-service/src/main/java/botto/xmpp/connectors/mock/MockConnector.java
	botto-service/src/main/java/botto/xmpp/connectors/mock/MockConnectorConfiguration.java
	botto-service/src/main/java/botto/xmpp/engine/MockEngineMain.java