Fixed #12694 -- Added template block to make it easier to add new tools to the...

Fixed #12694 -- Added template block to make it easier to add new tools to the change_list and change_form templates. Thanks to andybak for the suggestion, and Simon Meers for the final patch.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@14795 bcc190cf-cafb-0310-a4f2-bffc1f526a37