Uniformize and clean boxes behaviour and translation.

htdocs/admin/boxes.php

htdocs/core/boxes/box_commandes.php

htdocs/core/boxes/box_factures.php

htdocs/core/boxes/box_factures_fourn.php

htdocs/core/boxes/box_ficheinter.php

htdocs/core/boxes/box_propales.php

htdocs/core/boxes/box_supplier_orders.php

htdocs/core/class/infobox.class.php

htdocs/core/modules/modCommande.class.php

htdocs/langs/en_US/boxes.lang

htdocs/langs/fr_FR/boxes.lang

htdocs/user/class/user.class.php