LUCENE-5801: add back OrdinalMappingAtomicReader

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/trunk@1607582 13f79535-47bb-0310-9956-ffa450edef68
LUCENE-5801: move test under correct package

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/trunk@1607585 13f79535-47bb-0310-9956-ffa450edef68
reverting SOLR-5473 , SOLR-5474

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/trunk@1607587 13f79535-47bb-0310-9956-ffa450edef68