title: create xml with jdom, how to set standalone="no" attribute
body: <p>When I create a jdom document (Document doc = new Document();), by default I only see version and encoding in the xml header:</p>
  
  <pre><code>&lt;?xml version="1.0" encoding="utf-8" ?&gt;
  </code></pre>
  
  <p>How can I add the standalone attribute to get:</p>
  
  <pre><code>&lt;?xml version="1.0" encoding="utf-8" standalone="no" ?&gt;
  </code></pre>