It turns out that imho when talking about application groups (identified
by name) and application instances it's just logical to speak of
instances and applications. So the Application class get's renamed to
Instance. So an Application is now a set of Instances with the same name

* extract InfoUpdater from StatusUpdater
* rename ApplicationJournal to ClientApplicationEventStore
* ClientApplicationEventStore now implements reactor's Publisher
* Reworked AdminApplicationTest to be more sophisticated.