Merge branch 'melinath'

* melinath:
  Pre-merge cleanup.
  Switched URLRedirectValidator and URLLinkValidator to subclass directly from RegexValidator. --Avoids having to implement verify_exists for a link on a node that, say, might not even be on a site per se. If that's something I want later, I can look at it then... for now, this will fulfill its function just fine.
  Explicated DoesNotExist exception for PageAdmin save_model method.
  Added get_path fallback to slug to increase information flow by reducing the number of ? displayed
  Revert Redirect unicode.
  Added Redirect unicode.
  Added redirect and link validators to allow internal-style absolute and relative links/redirects.
  Fixed null content reference id bug.