OAK-1640: When modifying node types, revalidate only affected content

git-svn-id: https://svn.apache.org/repos/asf/jackrabbit/oak/trunk@1582863 13f79535-47bb-0310-9956-ffa450edef68
Update oak-mk-perf to 0.20-SNAPSHOT
Drop unused class

git-svn-id: https://svn.apache.org/repos/asf/jackrabbit/oak/trunk@1582864 13f79535-47bb-0310-9956-ffa450edef68