title: Send choice Value instead choice key from Symfony form
body: <p>I need to send from Symfony form <strong>ChoiceType::class</strong></p>
  
  <p>But I don't need choices keys, I need to send choices values.</p>
  
  <p>Is that is possible?</p>
  
  <pre><code> $form-&gt;add('section', ChoiceType::class, array(
                  'mapped' =&gt; false,
                  'choices' =&gt; array(
                      1 =&gt; 'value1',
                      2 =&gt; 'value2'
  
                  ),
            ));
  </code></pre>
  
  <p>I just want to send value1 if I chose <strong>value1</strong>,</p>
  
  <p>not <strong>key 1</strong> as default.</p>