title: selenium : how to know if a qooxdoo button is enable or not
body: <p>We are using qooxdoo 5.0.2 and selenium for our functional tests.
  We try to find a way in selenium to know (html/style/xpath/...) if a QX button is enable/disable.
  When We inspect both QX buttons (enable &amp; disable), it seems there is no difference.
  Any way to distinguish that, please ?</p>
  <p>Thanks in advance for your help.</p>