LUCENE-5810: NRTCachingDirectory now implements FilterDirectory

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/branches/branch_4x@1609202 13f79535-47bb-0310-9956-ffa450edef68
LUCENE-5714: Enhance TestBBoxStrategy with/without docvalues & indexed

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/branches/branch_4x@1609210 13f79535-47bb-0310-9956-ffa450edef68