OAK-798: Review / refactor TreeImpl and related classes
reduce usage of deprecated API: replace getLocation with getTree and exists

git-svn-id: https://svn.apache.org/repos/asf/jackrabbit/oak/trunk@1477955 13f79535-47bb-0310-9956-ffa450edef68
OAK-798: Review / refactor TreeImpl and related classes
reduce usage of deprecated API: replace getLocation with getTree and exists, replace usages of TreeLocation with Tree in oak-jcr

git-svn-id: https://svn.apache.org/repos/asf/jackrabbit/oak/trunk@1477956 13f79535-47bb-0310-9956-ffa450edef68