Pass user (if set by authenticate) to ascoltatore. This is useful, for example,
when each sensor authenticates using different credentials.
Pass packet and client to ascoltatore in mosca property of options when publishing.
Don't use published messageId when sending packet to client since it's
unique to the connection.
Merge pull request #30 from davedoesdev/pass_username_to_ascoltatore

Pass MQTT details when publishing to Ascoltatori.