title: a4j:commandbutton with only icon and no text
body: <p>How can I show icon on the a4j:commandButton. <br>I don't want text on the button.</p>
  
  <pre><code>&lt;a4j:commandButton id="editLink" styleClass="buttonImage"
                     action="#{bean.populateForm}"
                     oncomplete=" #{rich:component('EditPopup')}.show();"
                     render="EditPopup" execute="@form"&gt;
  &lt;/a4j:commandButton&gt;
  </code></pre>
  
  <p>and below code for styleClass</p>
  
  <pre><code> .buttonImage   {background-image: url(../images/edit.gif)!important}
  </code></pre>