Fixed #16873 - Added dummy database backend in default settings, so that just importing django.db doesn't trigger ImproperlyConfigured if there is no DATABASES setting.
Fixed #16873 - Added dummy database backend in default settings, so that just importing django.db doesn't trigger ImproperlyConfigured if there is no DATABASES setting.

git-svn-id: 554f83ef17aa7291f84efa897c1acfc5d0035373@16946 bcc190cf-cafb-0310-a4f2-bffc1f526a37

svn2github/django,svn2github/django,svn2github/django