Fixed doc references to `django.db.models.query.QuerySet` and converted some...

Fixed doc references to `django.db.models.query.QuerySet` and converted some tabs that were introduced in r16699 to spaces.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@16915 bcc190cf-cafb-0310-a4f2-bffc1f526a37