title: add link to change page using raw_id_fields in django admin
body: <p>Is there any chance to add link to change page of a Foreign key object next to 'raw_id_fields' in django admin?
  I use raw_id_fields to reduce number of queries to mysql.
  I could edit or add a foreign key object when I didn't use raw_id_fields. </p>
  
  <p>How to do it with raw_id_fields?</p>
  
  <p>@AntoinePinsard, I've tried the second solution. The field 'Edit My FK' was created but there is nothing except for a hyphen.</p>
  
  <p>That's my modeladmin.</p>
  
  <pre><code>class FlatAdmin(admin.ModelAdmin):
      inlines = [NeedInline]
      readonly_fields = ('flat_house_edit_link',)
      raw_id_fields = ('flat_house',)
      list_display = ('show_date','show_block','show_house','show_rooms','show_price','show_stage')
      list_filter = ('flat_house__house_block','flat_rooms')
      search_fields = ('flat_house__id',)
  
      field = ['flat_house','flat_house_edit_link','flat_owner','flat_price','flat_rooms','flat_total_sq','flat_life_sq','flat_kitchen_sq','flat_floors']
  
      def flat_house_edit_link(self, instance):
          if instance:
              fk_id = instance.user_id
          else:
              fk_id = None
          if fk_id:
              opts = instance._meta.get_field('flat_house').rel.model._meta
              related_url = reverse(
                  'admin:{}_{}_change/?_to_field=id&amp;_popup=1'.format(
                       opts.ha,
                       opts.house,
                  ),
                  args=[fk_id],
              )
              return format_html(
                   '&lt;a target=_blank href="{}"&gt;Go!&lt;/a&gt;', related_url)
          else:
              return "No related object"
      flat_house_edit_link.short_description = "Change house"
  admin.site.register(Flat,FlatAdmin)
  </code></pre>