Fixed #14390 and #16262 -- Moved password related functions from auth models...

Fixed #14390 and #16262 -- Moved password related functions from auth models to utils module and stopped check_password from throwing an exception. Thanks, subsume and lrekucki.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@16456 bcc190cf-cafb-0310-a4f2-bffc1f526a37