SOLR-4746: fix JSON output for distributed grouping top level

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/trunk@1470523 13f79535-47bb-0310-9956-ffa450edef68
SOLR-3251: Dynamically add fields to schema.

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/trunk@1470539 13f79535-47bb-0310-9956-ffa450edef68