title: django admin form with predefined inlines
body: <p>The problem is to have the inline models to have some of theirs fields preselected according to other model.</p>
  
  <p>Let's make an example:</p>
  
  <pre><code>class Document(models.Model):
      DOC_TYPES = ((DC1, 'Doc type 1'), (DC2, 'Doc type 2'))
      doctype = model.CharField(choices=DOC_TYPES, default=DC1)
  
  class OptionCategory(models.Model):
      name = model.CharField()
  
  class Option(models.Model):
      document = models.ForeignKey(Document)
      option_category = models.ForeignKey(OptionCategory)
      some_data = models.CharField()
  </code></pre>
  
  <p>Assume that option is defined inline in document model admin.</p>
  
  <p><code>OptionCategory</code> is necessary - those may be added by admin - I'd like to have a creation form for Document with so many option models in inline forms as there is option categories. This can be achieved easily using extras in <code>Option</code> model admin. The questions are:</p>
  
  <ol>
  <li>How to present inline fields each with different option category preselected?</li>
  <li>How to change options dynamically (basing on <code>Document.doctype</code> after adding similar doctype field in <code>OptionCategory</code>) - preferably with ajax?</li>
  </ol>