Edit Checklist should show old checklist

[lramos15]

Currently create checklist and edit checklist are sort of the same thing as they do a diff, but there is no way to know what the current checklist has in that view. We should make the edit checklist experience easier by showing the user the current checklist and allowing them to add and remove stuff from there. Note: if things are removed they are only marked as inactive and not deleted so that old checklists don't get invalidated.