Fix for APLO-245: The LevelDB store does not seem to get cleaned/compacted

Posting to '/virtual-hosts/{id}/store/action/compact' will now compact the store.

git-svn-id: https://svn.apache.org/repos/asf/activemq/activemq-apollo/trunk@1435245 13f79535-47bb-0310-9956-ffa450edef68