OAK-1915: TarMK Cold Standby

Improved MBeans, added documentation.


git-svn-id: https://svn.apache.org/repos/asf/jackrabbit/oak/trunk@1626168 13f79535-47bb-0310-9956-ffa450edef68
@trivial: updated oak-run readme file adding descriptions of the runmodes syncmaster and syncslave

git-svn-id: https://svn.apache.org/repos/asf/jackrabbit/oak/trunk@1626175 13f79535-47bb-0310-9956-ffa450edef68