[IMP] payment addons: fixed submit buttons: now have type=submit (and not image or...

[IMP] payment addons: fixed submit buttons: now have type=submit (and not image or nothing) and removed name, because this may cause issues when trying to submit a form manually with type=submit and a name. Also improved js code in website_sale to correctly handle the click binding, the asynchronous call to the server to create the transaction, and then submit the form. As form submission is synchronous in javascript, we cannot use the deferred. Instead we prevent the click event from bubbling, wait for the server to create the transaction, adn then manually submit the form.