Rename

git-svn-id: https://svn.apache.org/repos/asf/jena/trunk@1530531 13f79535-47bb-0310-9956-ffa450edef68
Tidy up null and singleton set/map/list

git-svn-id: https://svn.apache.org/repos/asf/jena/trunk@1530546 13f79535-47bb-0310-9956-ffa450edef68
Merge remote-tracking branch: upstream/trunk