OAK-672: Avoid JCR APIs calling other JCR APIs
Move Delegate classes to new package delegate

git-svn-id: https://svn.apache.org/repos/asf/jackrabbit/oak/trunk@1454621 13f79535-47bb-0310-9956-ffa450edef68
OAK-672: Avoid JCR APIs calling other JCR APIs
Extend SessionOperation with preconditions

git-svn-id: https://svn.apache.org/repos/asf/jackrabbit/oak/trunk@1454622 13f79535-47bb-0310-9956-ffa450edef68