Fixed createConfirmBox to allow prompt=0 (with initial_nick or url nick)

The function createConfirmBox previously only created a submit button with no form element, and no events bound to the button.  This commit fixes that by adding a form element, adding the submit button to the form, and adding a simple event bound to the button.

This allows you to do ?nick=XXXX&channels=help&prompt=0 to pass in all the parameters you need to connect.