The modification to action_recalculate_partners_name prevents the _inverse_name method from
triggering when recalculating the names of partners, leaving the firstname, lastname and
lastname2 fields intact.
Display the recompute button only after saving the settings if the order hase changed. Once the recompute is done, the buttons desapears.
Bedore this change it was not possible to recompute the partner names order since the button was only displayed after changing the order value but before saving the changes. When clicked, an error message was displayed since the action will force the reload of the page before saving the values...