refs #1054
  Added a timeout using Timeout class from ruby.
  We wait 10 seconds, if the bind to the LDAP server does not returns,
  a message is sent to the user warning the LDAP server is unreachable.
  The error is logged to the server log file.
refs #1076
refs #1077

Removed the ldap authentication option from login view.
Made sure that ldap authentication is the first to be executed if it is enabled on the site.
Made sure that if ldap is enabled and the authentication process fails, it executes the standard authentication.