SOLR-4909: Use DirectoryReader.openIfChanged in non-NRT mode

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/trunk@1521556 13f79535-47bb-0310-9956-ffa450edef68
SOLR-5210: make perSegFilter cache actually per-segment

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/trunk@1521559 13f79535-47bb-0310-9956-ffa450edef68
SOLR-5227: Correctly fail schema init if a dynamicField is configured to be required, or have a default value

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/trunk@1521587 13f79535-47bb-0310-9956-ffa450edef68