Merging code for SOLR-4196, SOLR-4401, SOLR-4525. All about obsoleting solr.xml and supporting a large number of cores

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/branches/branch_4x@1454477 13f79535-47bb-0310-9956-ffa450edef68