Fixed #21386 -- Removed admindocs dependence on sites framework

* Removed ADMIN_FOR setting and warn warning
* Group view functions by namespace instead of site
* Added a test verifying namespaces are listed

Thanks to Claude Paroz for reviewing and ideas for improvement.

tests/admin_docs/urls.py

@@ -1,11 +1,16 @@
-from django.conf.urls import include, patterns
+from django.conf.urls import include, patterns, url
 from django.contrib import admin
 
 from . import views
 
+ns_patterns = patterns('',
+    url(r'^xview/func/$', views.xview_dec(views.xview), name='func'),
+)
+
 urlpatterns = patterns('',
     (r'^admin/', include(admin.site.urls)),
     (r'^admindocs/', include('django.contrib.admindocs.urls')),
+    (r'^', include(ns_patterns, namespace='test')),
     (r'^xview/func/$', views.xview_dec(views.xview)),
     (r'^xview/class/$', views.xview_dec(views.XViewClass.as_view())),
 )