OAK-685 Enforce referential integrity for referenceable nodes
 - introduced the multiple value properties again
 - added the property name to the stored path to help with OAK-1137




git-svn-id: https://svn.apache.org/repos/asf/jackrabbit/oak/trunk@1541659 13f79535-47bb-0310-9956-ffa450edef68