OAK-2298 - LuceneIndex should provide correct cost based on index size

If query involves fulltext then estimatedEntryCount would reflect numOfDoc (unless entryCount is explicitly configured, default value is not considered). For property indexes min of entryCount and numOfDocs would be used (default entryCount set to 1000)

git-svn-id: https://svn.apache.org/repos/asf/jackrabbit/oak/trunk@1642031 13f79535-47bb-0310-9956-ffa450edef68