title: proxy without authentication in settings.xml
body: <p>I am looking for a way to set system proxy settings in settings.xml. If the proxy server does not need authentication, can I leave the username and password tag blank ? How can I achieve this ?</p>
  
  <p>I can not find any documents from maven on this : <a href="http://maven.apache.org/guides/mini/guide-proxies.html" rel="nofollow">http://maven.apache.org/guides/mini/guide-proxies.html</a></p>