LUCENE-3069: move CHANGES entries under 4.7

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/trunk@1562498 13f79535-47bb-0310-9956-ffa450edef68
LUCENE-3069: merge the back-compat indices from 4.x

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/trunk@1562506 13f79535-47bb-0310-9956-ffa450edef68