title: FOSUserBundle sending more email on user creation
body: <p>I'm developing a web site using Symfony2 and I'm using FosUserBundle to manage the users.</p>
  
  <p>On user registration I'd like to send a mail to admins to inform of the event.
  I followed the official <a href="https://github.com/gimler/FOSUserBundle/blob/master/Resources/doc/emails.md" rel="nofollow">FOS manual</a> but I'm not able to override correctly the mail sending and anyway I don't know how to generate a new email for the admins.</p>
  
  <p>The first problem comes from the <code>config.yml</code> files where I set the following params for the Mailer override</p>
  
  <pre><code># ...
  fos_user:
          registration:
              confirmation:
                  enabled: true
              email:
                  template: UserBundle:Registration:confirmation.email.twig
              form:
                  type: user_registration
  </code></pre>
  
  <p>The <code>email:</code> and <code>template:</code> rows gave me the following errors:</p>
  
  <pre><code>[Symfony\Component\Config\Definition\Exception\InvalidConfigurationException]  
  Unrecognized option "email" under "fos_user.registration"
  </code></pre>
  
  <p>Any advice on how to solve the problem and any other on how to implement the second mail sending?</p>