OAK-1338: Implement QueryStat from Jackrabbit API
Implement repository statistics: session login count and session count

git-svn-id: https://svn.apache.org/repos/asf/jackrabbit/oak/trunk@1565273 13f79535-47bb-0310-9956-ffa450edef68
OAK-1338: Implement QueryStat from Jackrabbit API
Implement repository statistics: session read and write statistics

git-svn-id: https://svn.apache.org/repos/asf/jackrabbit/oak/trunk@1565276 13f79535-47bb-0310-9956-ffa450edef68