Purpose of this commit is to ease the use of the payment widget and
avoid having to perform too much custom code in the various routes used
when doing payments :
* when instantiating the widget give him its parent element data so
that parameters given when calling the payment form template are
automatically present in the widget options;
* support more parameters when calling the route for form-based acquirers
including access_token, URLs and callback method;
* when doing a form-based payment a call to a JSON route returning the
rendered form is done. Payment widget now uses all data from that
form including the URL of the acquirer website. This way form-based
acquirers are really dynamic and values update is easier;
* remove hidden display of form-based acquirers as all data come now
from the called JSON route that returns the form;
* add a warning about partner-id not being set as it is an issue some
people may encounter;
Thibault Delavallée
06fe263a15