Adopt SummerCMS v0.1.1 admin features

Datepickers on native time.Time / lagoon.Date fields, file uploads on
materials, readings and class sessions managed from the course form
(course_id made nullable).

controllers/api/calendar.go

@@ -75,7 +75,7 @@ func (h *Handlers) newFeedJSON(r *http.Request, f *models.CalendarFeed) calendar
 		IncludeDeadlines:  f.IncludeDeadlines,
 	}
 	if f.LastFetchedAt != nil {
-		s := string(models.NewDateTime(*f.LastFetchedAt))
+		s := models.FormatDateTime(*f.LastFetchedAt)
 		out.LastFetchedAt = &s
 	}
 	return out