OAK-1418: Read performance regression

Keep track of the last access time in the SessionDelegate instance
so we won't need to rely on side-effects in RefreshStrategy.needsRefresh()

git-svn-id: https://svn.apache.org/repos/asf/jackrabbit/oak/trunk@1574520 13f79535-47bb-0310-9956-ffa450edef68
OAK-1418: Read performance regression

Avoid one method call on the critical path in NamePathMapperImpl

git-svn-id: https://svn.apache.org/repos/asf/jackrabbit/oak/trunk@1574521 13f79535-47bb-0310-9956-ffa450edef68