LUCENE-5752: improve tests; move isEmpty out of LA into BasicOps; BasicOps.sameLanguage requires no dead states; rename LA.finish -> finishState

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/branches/lucene5752@1602966 13f79535-47bb-0310-9956-ffa450edef68