Added a sort to the historical view of snapshots

Sorting by reverse order of snapshot creation date. We don't really
care about records with no snapshot, so the resulting inner join isn't
a problem.

After many attempts to test this, I gave up, because criteria just
doesn't work with unit tests.
Sort historical snapshots for a subject in reverse date order

Passing the sorted collection in the model now, rather than accessing
it from the Subject in the view.