OAK-2261 - Enable support for NodeType based indexing rules (WIP)

Remove dependency on ImmutableRoot (as it is part of o.a.j.oak.core package which is not exported)

git-svn-id: https://svn.apache.org/repos/asf/jackrabbit/oak/trunk@1639577 13f79535-47bb-0310-9956-ffa450edef68