Remove `_links` element from FoxyCart responses

remove_foxy_links.php

function removeLinks($order) {
    foreach ($order as $key=>$el) {
        if (is_array($el)) {
            if ($key === '_links') {
                unset($order[$key]);
            }
            else {
                $order[$key] = removeLinks($el);
            }
        }
    }
    return $order;
}