* Use @EventListener instead of ApplicationListener-interface
 * Don't inherit ClientApplicationEvent from ApplicationEvent - so JournaledEvent isn't needed anymore
 * added eclipse formatter rules
 * reformatted all files

The health-check is made at a fixed interval (default: 10s) for all expired status-information (default-lifetime: 30s).
The application health-endpoint must either respond with a JSON-Body having a status-field or with an empty body and all 2xx-http-responses are interpreted as UP and every other status as DOWN.

To enable, you just have to add a DiscoveryClient to your Spring Boot Admin Server.
Also did some code polish.
Closes #44

Fixes #27

Rename ApplicationStore methods to spring-data-style

* Separate AppStore from AppRegistry
* Allow Id generation to be altered
* Remove logic from Application; Move id genretation into AppRegistry
* Make AppStore threadSafe