title: how do I replace the django admin add page
body: <p>I'm using Django 1.4 and Grappelli</p>
  
  <p>I need an admin add page that is totally different from the change page on the same model. Different fieldsets, different readonly_fields (actually none for add), different inlines (actually none for add). 
  And when it's submitted I need to direct it off to a factory function instead of going down the normal create path.
  But I need it to look and act like an admin page, and I particularly need foreign key selectors like I'd get on a normal admin page.</p>
  
  <p>I tried messing around with get_readonly_fields and friends for a while but get_inline_instances is 1.5 only and I couldn't find another hook for removing the inlines.</p>
  
  <p>Then I tried replacing the view and the form using get_urls but I couldn't figure out what needed to go into the context to make the template render.</p>
  
  <p>I also tried messing with get_form, but the ModelAdmin still expects the form to have the same fields.</p>
  
  <p>Is one of these heading in the right direction? does anyone know what I need to do?</p>