title: add extra field to ModelForm
body: <p>I am adding an extra field to a Django ModelForm like that:</p>
  
  <pre><code>class form(forms.ModelForm):
      extra_field = forms.CharField(label='Name of Institution')
      class Meta:
          model = db_institutionInstitution
          fields = ['conn_kind','time','inst_name2']
  </code></pre>
  
  <p>The form is actually working fine, but I cant prepopulate it. I use it in a <code>modelformset_factory</code>:</p>
  
  <pre><code>formset = modelformset_factory(db_institutionInstitution,form=form)
  </code></pre>
  
  <p>I manually run through a queryset and add the entry in the dictionary needed for the additional form in the formset. However, when I call:</p>
  
  <pre><code>formset1 = formset(prefix='brch',queryset=qs1)
  </code></pre>
  
  <p>the <code>extra_field</code> is not prepopulated as intended (the rest is working fine).</p>
  
  <p>Can anyone help?</p>