OAK-1973 - IndexUpdate traverses the data nodes under index nodes

– Wraps the IndexUpdate with VisibleEditor where used (except Upgrade)
– Removed internal wrapping of editors as the IndexUpdate itself is wrapped

git-svn-id: https://svn.apache.org/repos/asf/jackrabbit/oak/trunk@1611584 13f79535-47bb-0310-9956-ffa450edef68