Notification service implementation based on RabbitMQ

This is going to work in conjuction with Dovecot plugin for Openchange
and also notification consumer implemented in Openchange

So we have:
* Dovecot plugin for Openchange. Whenever new message arrives,
  it pushes a message in RabbitMQ
* Daemon (provided by this patch) listens for such RMQ messages
  and register them into mapistore indexing
* When message is registered we publish RMQ message into
  user specific queue
* TODO: A consumer in Openchage layer consumes such messages
  and notify Outlook for changes - not fully implemented yet.

NOTE: We should have RMQ message handler implemented into Openchange
      for this to work.
Just discuss this with @kernevil - this requirement comes from rabbitmq
Possible approaches (all credit goes to @kernevil )
* compile rabbitmq w/o SSL - I am not sure how painful that would be
* this for this later :)
* forget about rabbitmq (this is mine - considering other approaches would make sense imo)

@jkerihuel @jelmer any comment from guys would be highly appreciated