OAK-535 - MergeCommand reads complete tree into memory

-Further optimization to MergeCommand optimization. Basically, even if there have been commits on trunk since the branch was created, MergeCommand now checks whether those commits are conflicting with branch commits and if not, it simply reapplies branch commits to trunk.
-Added average time for MK operations in TimingWrapper

git-svn-id: https://svn.apache.org/repos/asf/jackrabbit/oak/trunk@1433984 13f79535-47bb-0310-9956-ffa450edef68