Fixed "verifyCredentials" function

Changed: loadBy -> tryLoadBy so exception won't be thrown on the "Front-end Authorization" index page when the user is trying to login with non existing user. (loadBy throws exception when no rows are returned)
IMO: lines 168-178 (the whole verifyCredentials) shouldn't exist as it overides the better done Auth/Basic authentication (as it doesn't handle encrypted passwords at all)