title: Symfony2 Forms : Changing the default prefix in Form Labels
body: <p>I am rendering a form, and every widget has an ID like : form_username, form_password, etc
  and every corresponding label has a <strong>for</strong> field as for="form_username"</p>
  
  <p>can I customize this ID and For attribute pair? Because I am rendering 2 forms on a page, and their field names are clashing...</p>
  
  <p><strong>edit</strong> : Here is an example code where I want to customize the Form Name.</p>
  
  <pre><code>$form = $this-&gt;createFormBuilder($user, array('validation_groups' =&gt; array('registration')))
               -&gt;add('username', 'text')
               -&gt;add('email', 'email')
               -&gt;add('password', 'repeated', array('type' =&gt; 'password'))
               -&gt;getform();
  </code></pre>