Correct usage message

git-svn-id: https://svn.apache.org/repos/asf/jena/trunk@1530627 13f79535-47bb-0310-9956-ffa450edef68
Tidy up comments

git-svn-id: https://svn.apache.org/repos/asf/jena/trunk@1530744 13f79535-47bb-0310-9956-ffa450edef68
Merge remote-tracking branch: upstream/trunk