SOLR-6704: Added unit tests that uncovered TrieDateField bug in branch 4.10.x

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/trunk@1636980 13f79535-47bb-0310-9956-ffa450edef68
SOLR-6684 Fix-up /export JSON

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/trunk@1636986 13f79535-47bb-0310-9956-ffa450edef68