title: Django models.ForeignKey filter
body: <p>I have a 2 models:</p>
  
  <pre><code>class Foo(models.Model):
      name...
      type = models.CharField(choices=TYPE_CHOICES)
  
  class Fighter(models.Model):
      foo = models.ForeignKey(Foo, filter(type="A")
  </code></pre>
  
  <p>Can you filter the drop down list of the foreign key?</p>