Create a mechanism to automatically refresh stale forms

All of the work gone into this module is great, but it doesn't prevent edge cases where forms may become stale despite a page's cache living on (either in Drupal's page cache, or in an external cache).

The end-result is a period during which AJAX requests triggered on the country field fail; to the end-user, this manifests as perceived cultural ineptitude (e.g. "I selected country Y, which doesn't have country X's states).

We should be able to detect when this state has happened (before a user triggers an AJAX request), and correct it if it happens, without inconveniencing the user in any way.