SOLR-6523: Provide SolrJ support for specifying stateFormat while creating Collections

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/trunk@1646558 13f79535-47bb-0310-9956-ffa450edef68
SOLR-6523: Fixing the test. Removing the unwanted check and calls

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/trunk@1646567 13f79535-47bb-0310-9956-ffa450edef68
SOLR-6864: Support registering searcher listeners in SolrCoreAware.inform(SolrCore) method

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/trunk@1646577 13f79535-47bb-0310-9956-ffa450edef68