title: django: how does manytomanyfield with through appear in admin?
body: <p>As stated in the title how does <code>manytomanyfield</code> with <code>through</code> appear in the admin site? </p>
  
  <pre><code>class SchoolClass(models.Model):
      id = models.AutoField(primary_key = True)
      class_name = models.TextField()
      level = models.IntegerField()
      taught_by = models.ManyToManyField(User,related_name="teacher_teaching",through='TeachSubject')
      attended_by = models.ManyToManyField(User,related_name='student_attending')
  
      def __unicode__(self):
          return self.class_name
      class Meta:
          db_table = 'classes'
  
  
  class TeachSubject(models.Model):
      teacher = models.ForeignKey(User)
      class_id  = models.ForeignKey(SchoolClass)
      subject = models.ForeignKey(Subject)
  </code></pre>
  
  <p>In the admin site, for the model <code>SchoolClass</code>, I have a field for attending students, but not the teachers.</p>