OAK-603: Use Microkernel.rebase in oak-core instead of reimplementing it

git-svn-id: https://svn.apache.org/repos/asf/jackrabbit/oak/trunk@1441467 13f79535-47bb-0310-9956-ffa450edef68
OAK-548: Moving larger trees cause OutOfMemoryError
fixed since rebasing is now handled in the Microkernel

git-svn-id: https://svn.apache.org/repos/asf/jackrabbit/oak/trunk@1441469 13f79535-47bb-0310-9956-ffa450edef68