[IMP] website_sale: show alert (error) message if VAT number, Email is invalid.

Give a proper error message, if users enter invalid VAT number as well as check email address is in valid format. 

<b>Task:</b> https://www.odoo.com/web#id=9970&view_type=form&model=project.task&menu_id=3942&action=327
<b>Pad:</b> https://pad.odoo.com/p/r.5xdH8OsRKzEJJzl9
You should refactor the error structure. A missing entry should be set to True (do it above). A missing entry or an incorrect entry that should trigger a message sets the dict entry to an error message. Example
error = {
  'name': True;
 'email': _('Invalid Email! Please enter a valid email address.')
}

In the template, add the error class if the key is set in the dict, and display all messages in the page header.