title: Django: ModelMultipleChoiceField doesn't select initial choices
body: <p>ModelMultipleChoiceField doesn't select initial choices and I can't make the following fix (link below) work in my example:</p>
  
  <p><a href="http://code.djangoproject.com/ticket/5247#comment:6" rel="noreferrer">http://code.djangoproject.com/ticket/5247#comment:6</a></p>
  
  <p>My models and form:</p>
  
  <pre><code>class Company(models.Model):
      company_name = models.CharField(max_length=200)
  
  class Contact(models.Model):
      company = models.ForeignKey(Company)
      first_name = models.CharField(max_length=100)
      last_name = models.CharField(max_length=100)
  
  class Action(models.Model):
      company = models.ForeignKey(Company, blank=True, null=True)
      from_company = models.ManyToManyField(Contact, verbose_name='Participant(s) from "Company"', blank=True, null=True)
  
  class Action_Form(ModelForm):
      from_company = forms.ModelMultipleChoiceField(queryset=Contact.objects.none(), widget=forms.CheckboxSelectMultiple())
      class Meta:
          model = Action
  </code></pre>
  
  <p>What I do and the results:</p>
  
  <pre>
  >>> contacts_from_company = Contact.objects.filter(company__exact=1) # "1" for test, otherwise a variable
  >>> form = Action_Form(initial={'from_company': [o.pk for o in contacts_from_company]}) # as suggested in the fix
  >>> print form['from_company']
  &lt;ul&gt;
  &lt;/ul&gt;
  >>> print contacts_from_company
  [&lt;Contact: test person&gt;, &lt;Contact: another person&gt;]
  
  >>> form2 = Action_Form(initial={'from_company': contacts_from_company})
  >>> print form2['from_company']
  &lt;ul&gt;
  &lt;/ul&gt;
  
  >>> form3 = Action_Form(initial={'from_company': Contact.objects.all()})
  >>> print form3['from_company']
  &lt;ul&gt;
  &lt;/ul&gt;
  </pre>
  
  <p>The way I was hoping it would work:<br>
  1. My view gets "company" from request.GET<br>
  2. It then filters all "contacts" for that "company"<br>
  3. Finally, it creates a form and passes those "contacts" as "initial={...}"  </p>
  
  <p><strong>Two questions:</strong><br>
  <strong>1. [not answered yet]</strong> How can I make ModelMultipleChoiceField take those "initial" values?<br>
  <strong>2. [answered]</strong> As an alternative, can I pass a variable to Action_Form(ModelForm) so that in my ModelForm I could have:</p>
  
  <pre>
  from_company = forms.ModelMultipleChoiceField(queryset=Contact.objects.filter(company__exact=some_id) # where some_id comes from a view
  </pre>