OAK-625 : Ability to pass workspace name to a CommitHook

moving init of security related commit hooks and validators to RootImpl to allow for run-time pluggability and multi-workspace setup.


git-svn-id: https://svn.apache.org/repos/asf/jackrabbit/oak/trunk@1447237 13f79535-47bb-0310-9956-ffa450edef68