LUCENE-5431: add FSLockFactory.toString() and fix FilterDirectory to override getLockID(); also change FSDirectory.toString() to use class.getSimpleName()

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/branches/branch_4x@1564305 13f79535-47bb-0310-9956-ffa450edef68