OAK-2317 : Detect nested authorizables introduced by change of primary type

git-svn-id: https://svn.apache.org/repos/asf/jackrabbit/oak/trunk@1643111 13f79535-47bb-0310-9956-ffa450edef68
OAK-2314: Mark checkpoints with relevant metadata
Add class name and thread to checkpoint info

git-svn-id: https://svn.apache.org/repos/asf/jackrabbit/oak/trunk@1643120 13f79535-47bb-0310-9956-ffa450edef68