LUCENE-5151: Associations aggregators enter an infinite loop if some documents have no category associations

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/trunk@1508440 13f79535-47bb-0310-9956-ffa450edef68
LUCENE-5149: CommonTermsQuery should allow minNrShouldMatch for high & low freq terms

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/trunk@1508453 13f79535-47bb-0310-9956-ffa450edef68
SOLR-5087, CoreAdminHandler.handleMergeAction generating NullPointerException. Thanks Patrick

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/trunk@1508476 13f79535-47bb-0310-9956-ffa450edef68