OAK-1114: Clarify NodeBuilder.moveTo() contract
The move succeeds if both, this builder and the new parent exist, there is no child with the given name at the new parent and the new parent is not in the subtree of this the source. After a successful move exists() of the moved builder returns false, otherwise it returns true.

git-svn-id: https://svn.apache.org/repos/asf/jackrabbit/oak/trunk@1535368 13f79535-47bb-0310-9956-ffa450edef68