Class.ActionRouter.php (closes #3463)

Also:
- added entry point `authent.php` to handle authentication instead of
  using `guest.php`.
Corrected localized message (refs #3463)
Renamed run() method ro runAuthenticationApp() (refs #3463)
Added `apacheAuthenticator` class (refs #3463)
Use `authent.php?logout` to perform logout (refs #3463)

Use `authent.php?logout` to dispatch action to AuthenticatorManager instead
of using hard-coded `app=AUTHENT&action=LOGOUT`.
Merge pull request #612 from eguaj/3.2-E3463

Class.ActionRouter.php (closes #3463)