Initial Contribution of the rollout-management feature

- Repository functionality for rollout, rolloutgroup entities
- Rollout scheduler to watch and handle running rollouts and start next
group of rollout
- Vaadin view to administrate rollouts and reflect the current rollout
status
- REST resources to cover rollout creation, updating, starting, pausing
and resuming

Signed-off-by: Michael Hirsch <michael.hirsch@bosch-si.com>

hawkbit-autoconfigure/src/main/java/org/eclipse/hawkbit/autoconfigure/eventbus/EventBusAutoConfiguration.java

@@ -12,6 +12,7 @@ import java.util.concurrent.Executor;
 
 import org.eclipse.hawkbit.eventbus.EventBusSubscriberProcessor;
 import org.eclipse.hawkbit.eventbus.EventSubscriber;
+import org.eclipse.hawkbit.repository.model.helper.EventBusHolder;
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.beans.factory.annotation.Qualifier;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;
@@ -54,4 +55,12 @@ public class EventBusAutoConfiguration {
         return new EventBusSubscriberProcessor();
     }
 
+    /**
+     * @return the singleton instance of the {@link EventBusHolder}
+     */
+    @Bean
+    public EventBusHolder eventBusHolder() {
+        return EventBusHolder.getInstance();
+    }
+
 }