Moved logic of children validation to the Persistent class.
Merge branch 'genie_v1api' of github.com:Netflix/genie into genie_v1api

Conflicts:
	genie-server/src/main/java/com/netflix/genie/server/resources/CommandConfigResourceV1.java
	genie-server/src/main/java/com/netflix/genie/server/services/impl/PersistentClusterConfigImpl.java
	genie-server/src/main/java/com/netflix/genie/server/services/impl/PersistentCommandConfigImpl.java