title: Can I change a Form Class action on build?
body: <p>On a form classe's <code>buildForm</code> method (<code>AbstractType</code> derived) can I set the action of that form? 
  What I want to do is similar to the <code>setAction</code> method that I can use when building an embedded form:</p>
  
  <pre><code>$form = $this-&gt;createFormBuilder()
    -&gt;setAction($this-&gt;generateUrl('my_action'))
    -&gt;add('field', 'text')
    -&gt;add('button', 'submit');
  </code></pre>
  
  <p>I mean, is the <code>setAction</code> an equivalent to form classes?</p>