[Web] Fix require_once to always include document root

[Web] Add system mails (send mails to all mailboxes via LMTP)
[Web] Allow to add more administrators
[Web] Fix domain administrator editing
[Web] Remove some foreign keys
[Web] Remove username from API
[Web] Remove more .php extension from code
[Web] More minor fixes

data/web/lang/lang.es.php

@@ -153,8 +153,6 @@ $lang['mailbox']['target_address'] = 'Dirección Goto';
 $lang['mailbox']['username'] = 'Nombre de usuario';
 $lang['mailbox']['fname'] = 'Nombre completo';
 $lang['mailbox']['filter_table'] = 'Filtrar tabla';
-$lang['mailbox']['yes'] = '✔';
-$lang['mailbox']['no'] = '✘';
 $lang['mailbox']['in_use'] = 'En uso (%)';
 $lang['mailbox']['msg_num'] = 'Mensaje #';
 $lang['mailbox']['remove'] = 'Eliminar';
@@ -259,7 +257,5 @@ $lang['admin']['save'] = 'Guardar cambios';
 $lang['admin']['admin'] = 'Administrador';
 $lang['admin']['admin_details'] = 'Editar detalles del administrador';
 $lang['admin']['unchanged_if_empty'] = 'Si no hay cambios dejalo en blanco';
-$lang['admin']['yes'] = '✔';
-$lang['admin']['no'] = '✘';
 $lang['admin']['access'] = 'Acceso';
 $lang['admin']['no_record'] = 'Sin registro';