QPID-5715: [Java Broker] Add virtual host node to the model and refactor existing broker functionality to conform the new model. Save configuration model version as VHN attribute and refactor the upgraders and configuration recovery.

git-svn-id: https://svn.apache.org/repos/asf/qpid/trunk@1588886 13f79535-47bb-0310-9956-ffa450edef68