title: Symfony2, Doctrine, update db entry without queryBuilder
body: <p>To save entry to db we can use:</p>
  
  <pre><code>$em-&gt;persist($entity);
  $em-&gt;flush();
  </code></pre>
  
  <p>But how can we update existing entry without using <code>$this-&gt;getEntityManager()-&gt;createQuery()</code> ? </p>
  
  <p>Can we? </p>
  
  <p>I'm searching some kind of <code>$em-&gt;update()</code> for existing entry in db.</p>