OAK-301 : oak docu

git-svn-id: https://svn.apache.org/repos/asf/jackrabbit/oak/trunk@1596231 13f79535-47bb-0310-9956-ffa450edef68
OAK-1822: NodeDocument _modified may go back in time

Revert changes because $max is only available in MongoDB 2.6

git-svn-id: https://svn.apache.org/repos/asf/jackrabbit/oak/trunk@1596233 13f79535-47bb-0310-9956-ffa450edef68