title: Symfony2: "Remember me" tries to authenticate by username instad of email
body: <p>I have an application with user authenticaton against database. The property I use is email:</p>
  
  <pre><code>    providers:
          administrators:
              entity: 
                class: CorabMainBundle:User
                property: email
  </code></pre>
  
  <p>Authentication works great!
  But I have huge problems getting the remember me functionality to work. 
  After several hours I think I found the problem but I don't know how to solve it...</p>
  
  <p>Symfony2 seems to try to authenticate with the username instead of email in case of remember me. </p>
  
  <p>dev.log says the following:</p>
  
  <pre><code>[2013-10-21 23:49:19] security.DEBUG: Remember-me cookie detected. [] []
  [2013-10-21 23:49:19] doctrine.DEBUG: SELECT t0.id AS id1, t0.username AS username2, t0.salt AS salt3, t0.password AS password4, t0.email AS email5, t0.is_active AS is_active6, t0.organisation AS organisation7 FROM User t0 WHERE t0.email = ? LIMIT 1 ["roger"] []
  [2013-10-21 23:49:19] security.INFO: User for remember-me cookie not found. [] []
  [2013-10-21 23:49:19] security.DEBUG: Clearing remember-me cookie "REMEMBERME" [] []
  </code></pre>
  
  <p>Line 2 is not ok beacuse it should not be <strong>roger</strong> but an <strong>email address</strong>. That's why the cookie gets deleted.</p>
  
  <p>How to tell symfony2 to use email as property for remember me authentication?</p>
  
  <p>Thank you for your help!</p>