Converted internal link generation in the admin and admin document generator to use named URLs.

Thanks to Florian Apolloner for both the initial patch and his final push to get
this fixed, to Dario Ocles for his great work on the admin templates and
switching the admin_doc application to also use named URLs, to Mikko Hellsing
for his comments and to Jannis and Julien for their review and design guidance.

Fixes #15294.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@16857 bcc190cf-cafb-0310-a4f2-bffc1f526a37