OAK-928: Read access is enforced on NEW items

Add isNew(String) and isReplaced(String) predicates for tracking the status of properties.
This allows us to skip read access checks on properties that were just added, even if they shadow existing content.

git-svn-id: https://svn.apache.org/repos/asf/jackrabbit/oak/trunk@1545803 13f79535-47bb-0310-9956-ffa450edef68