OAK-2200: Tune cost calculation for lucene property index
Added a configurable param entryCount which defaults to 1000 and indicates the max count to be returned by the lucene index.

git-svn-id: https://svn.apache.org/repos/asf/jackrabbit/oak/trunk@1634774 13f79535-47bb-0310-9956-ffa450edef68