DayDetail, the component, I used to use as a view. Now I'm swapping
things out so that DayDetailView handles the view itself. The DayDetail
component will still show the details of the day, but I'll create a
DayEditComponent which is dedicated to showing the edit interface for
everything in a day.
The swapping will now happen in DayDetailView, not in DayDetail or an
even deeper component.
This allows me to directly reference functions that occur on those
widgets without losing them behind a gtk::Widget upcast or needing to
later downcast them.
