Fix CHANGES.txt to reflect the twisted evolution and current state of the Admin UI "Files" conf directory File Browser.  (merged branch_4x r1570771)

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/branches/lucene_solr_4_7@1570772 13f79535-47bb-0310-9956-ffa450edef68