OAK-1266 - improved diagnostics and javadoc

git-svn-id: https://svn.apache.org/repos/asf/jackrabbit/oak/trunk@1596215 13f79535-47bb-0310-9956-ffa450edef68
OAK-301 : oak docu

git-svn-id: https://svn.apache.org/repos/asf/jackrabbit/oak/trunk@1596220 13f79535-47bb-0310-9956-ffa450edef68