title: Select ForeignKey field in form ChoiceField
body: <p>I have foreign key entries in my model that I'd like to use for my choicefields...now I'm not so sure how to go about this....my model file can be found <a href="https://stackoverflow.com/questions/1362426/get-foreign-key-value">here</a>  Basically I want have a choicefield for vehicle make, model, year, body style, exterior color and transmission.  Since all of them work in the same way I just need someone to point me in the right direction then I'm all set.</p>
  
  <pre><code>class Model(models.Model):
     model = models.CharField(max_length=15, blank=False)
     manufacturer = models.ForeignKey(Manufacturer)
     date_added = models.DateField()
     def __unicode__(self):
         name = ''+str(self.manufacturer)+" "+str(self.model)
         return name 
  
  class BodyStyle(models.Model):
     doors = models.PositiveSmallIntegerField()
     passengers = models.PositiveSmallIntegerField()
     style = models.CharField(max_length=15, blank=False)
     def __unicode__(self):
         name = str(self.doors)+" Door / "+str(self.passengers)+" Passenger / "+str(self.style)
         return name 
  </code></pre>