title: adding django admin many-to-many widget
body: <p>In the <a href="http://docs.djangoproject.com/en/dev/ref/contrib/admin/#working-with-many-to-many-models" rel="nofollow">django admin documentation</a>, it says the following:</p>
  
  <blockquote>
    <p>By default, admin widgets for many-to-many relations will be displayed on whichever model contains the actual reference to the ManyToManyField.</p>
  </blockquote>
  
  <p>Is there a way to get a similar widget to appear on the admin page for the other model, the one where the relationship isn't defined?</p>