Issue when creating large orders (multiple products) via the admin create order interface.

A strange issue this whereby the more products you add to the order (via the the admin order edit screen) the slower the AJAX response becomes, until you hit around 9 or 10 products at which point the request times out.

After some debugging I figured out the size of the form being built was growing exponentially with each product that was added, as the form was being pushed into the cache_form table this was causing speed issues as we end up pushing around several MB worth of form data ...

I've traced this down to the ship_to and bill_to order panes in the uc_order.order_pane.inc file - each time the form is being built, all the form_state['values'] are being added to the #default_value for the form element, when actually I *think* we should just be setting the default_value to be $form_state['values']['ship_to'] (or bill_to) ...

For example, I think

$form['ship_to'] = array(
        '#type' => 'uc_address',
        '#default_value' => isset($form_state['values']) ? $form_state['values'] : $order,
        '#required' => FALSE,
        '#attributes' => array('class' => array('uc-store-address-field')),
        '#key_prefix' => 'delivery',
);

should actually be

$form['ship_to'] = array(
        '#type' => 'uc_address',
        '#default_value' => isset($form_state['values']) ? $form_state['values']['ship_to'] : $order,
        '#required' => FALSE,
        '#attributes' => array('class' => array('uc-store-address-field')),
        '#key_prefix' => 'delivery',
 );

This at least stops the form from taking over the world, and it seems to not have broken the rest of the order handling :)