OAK-536: Implement rebase for branches in Microkernel
Add rebase method to MicroKernel interface. Implementations throw UnsupportedOperationException

git-svn-id: https://svn.apache.org/repos/asf/jackrabbit/oak/trunk@1441464 13f79535-47bb-0310-9956-ffa450edef68
OAK-536: Implement rebase for branches in Microkernel
implement rebase() for the H2 Microkernel

git-svn-id: https://svn.apache.org/repos/asf/jackrabbit/oak/trunk@1441465 13f79535-47bb-0310-9956-ffa450edef68