code: public JQMButton setRightButton(String text, String url) {
          return setRightButton(text, url, null);
      }
docs: Creates a new {@link JQMButton} with the given text and linking to the
  given url and then sets that button in the right slot. Any existing
  right button will be replaced.
  
  @param text
  the text for the button
  @param url
  the optional url for the button, if null then this button
  does not navigate by default
  
  @return the created button