Fix issue #461.

In the event that a checklist entry had an error, but the checklist
itself did not, the code would save the checklist and then fail to save
the entry formset.  Now, we validate both the checklist form and the entry
formset before we save ANYTHING, so this should prevent duplicate
situations.
Fix #461 for editing checklists.

For checklist edits, there was not a danger of duplicates, but changes
to checklists could be saved without entries being saved if there were
validation errors.  As with the New Checklist view, validate all forms
on the page before saving anything.