In an App Child, the All Things page is wrong

Summary: I think this is a side-effect of shadows. We're showing the parents of the concrete pages as Models, which we shouldn't be doing.

I also note that Simple Thing isn't displaying at all -- we're showing lots of separate little Models, rather than a proper hierarchy.

This may not be a problem of Apps per se: it may just be that we need to enhance the functions underlying the All Things page.