title: Remove default text from Symfony submit button
body: <p>This is my button which should be just icon without text</p>
  
  <pre><code>{{ form_widget(form.submit, { 'attr': {'class': 'fa fa-search'} }) }}
  </code></pre>
  
  <p>I tried also to set value in <strong>FormType</strong></p>
  
  <pre><code>-&gt;add('submit', 'submit', array(
                  'label' =&gt; '',
                  'attr' =&gt; array(
                      'value' =&gt; ''
                  )
              ))
  </code></pre>
  
  <p>But nothing happen, or to say better, button contain </p>
  
  <blockquote>
    <p>Submit</p>
  </blockquote>
  
  <p>default text</p>