[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.pt.php

@@ -140,8 +140,6 @@ $lang['mailbox']['target_address'] = 'Encaminhar para';
 $lang['mailbox']['username'] = 'Usuário';
 $lang['mailbox']['fname'] = 'Nome';
 $lang['mailbox']['filter_table'] = 'Procurar';
-$lang['mailbox']['yes'] = '✔';
-$lang['mailbox']['no'] = '✘';
 $lang['mailbox']['in_use'] = 'Em uso (%)';
 $lang['mailbox']['msg_num'] = 'Mensagens';
 $lang['mailbox']['remove'] = 'Remover';
@@ -239,7 +237,5 @@ $lang['admin']['save'] = 'Salvar';
 $lang['admin']['admin'] = 'Administrador';
 $lang['admin']['admin_details'] = 'Editar informações do administrator';
 $lang['admin']['unchanged_if_empty'] = 'Deixar em branco para não alterar';
-$lang['admin']['yes'] = '✔';
-$lang['admin']['no'] = '✘';
 $lang['admin']['access'] = 'Acessos';
 $lang['admin']['no_record'] = 'Nenhum registro';