Need a scheme for integrating formsets with pagetree's form handling

[nikolas]

I have a custom pageblock that manages a dynamic formset, and it's not clear how I would integrate that with pagetree's pre-generated <form>.

For example, when using the "change my answers" feature with a formset, I get the error: "ManagementForm data is missing or has been tampered with"

This is related to issue #44.