title: doctrine does not hydration when select custom fields
body: <p>i have tried select fields with doctrine query buidler.</p>
  
  <pre><code>$queryBuilder = $entityManager-&gt;createQueryBuilder();
  $queryBuilder-&gt;select('au.id, au.firstName')
      -&gt;from('Api\V1\Entity\AgencyUser', 'au')
      -&gt;orderBy('au.firstName', 'asc');
  $queryBuilder-&gt;andWhere('au.agency = :agencyId')
      -&gt;setParameter('agencyId', $agency-&gt;getId());
  
  print_r($queryBuilder-&gt;getQuery()-&gt;getResult(Query::HYDRATE_OBJECT));exit;
  </code></pre>
  
  <p>result :</p>
  
  <pre><code>Array
  (
      [0] =&gt; Array
      (
          [id] =&gt; 1
          [firstName] =&gt; agency
      )
  
  )
  </code></pre>
  
  <p>why this is an array ? i want to hydrated result. any idea ?</p>