[*] BO : Miss override form action

Hi,
In form.tpl, form action can be overrided by $submit_action var.

$submit_action is assigned in HelperForm.php, but in AdminController.php, the variable and the assignment of the variable HelperForm->submit_action is missing.
This is usefull for generate Form with different action that add-Table-.
Thanks
Merge pull request #1501 from ccauw/patch-16

[*] BO : Miss override form action