Removed some import-time dependencies on Django's settings.

Now you can import the file storage stuff and still call settings.configure()
afterwards. There is still one import-time usage of settings in
django.contrib.comments, but that's unavoidable.

Backport of r9945 and r9946 from trunk (this is needed in order to fix #8193 in
a clean fashion, which is why it's being backported).

git-svn-id: http://code.djangoproject.com/svn/django/branches/releases/1.0.X@9947 bcc190cf-cafb-0310-a4f2-bffc1f526a37