Javadoc syntax fixes

git-svn-id: https://svn.apache.org/repos/asf/jena/trunk@1616242 13f79535-47bb-0310-9956-ffa450edef68
Add new line at end of writing

git-svn-id: https://svn.apache.org/repos/asf/jena/trunk@1616243 13f79535-47bb-0310-9956-ffa450edef68
Only print {} for default graph if not empty

git-svn-id: https://svn.apache.org/repos/asf/jena/trunk@1616244 13f79535-47bb-0310-9956-ffa450edef68