New: Add message to explain how to use the page. Make things more clear

for user.

htdocs/commande/liste.php

@@ -417,8 +417,10 @@ if ($resql)
 
 	print '</table>';
 
-	print '</form>';
+	print '</form>'."\n";
 
+	print '<br>'.img_help(1,'').' '.$langs->trans("ToBillSeveralOrderSelectCustomer", $langs->transnoentitiesnoconv("CreateInvoiceForThisCustomer")).'<br>';
+	
 	$db->free($resql);
 }
 else

htdocs/langs/en_US/orders.lang

@@ -164,3 +164,4 @@ Ordered=Ordered
 OrderCreated=Your orders have been created
 OrderFail=An error happened during your orders creation
 CreateOrders=Create orders
+ToBillSeveralOrderSelectCustomer=To create an invoice for several orders, click first onto customer, then choose "%s".