Make scheduling preparation easier

• This implements #144 (closed)
  • Don't show slots, slot creation button, and availabilities for wishes on detail page
  • Don't create slots for wishes automatically (and don't ask for durations)
  • Automatically create one slot when wish changes to AK
  • Automatically remove all unscheduled slots when AK changes to wish
• Introduce new generic admin actions with intermediate pages (preview/confirmation)
• Implements #145 (closed)
  • Admin interaction to delete slots for wishes
  • Admin interaction to create default availabilities
• Speedup and improve view for attention requiring AKs

AKModel/models.py

@@ -335,14 +335,6 @@ class AK(models.Model):
     def availabilities(self):
         return "Availability".objects.filter(ak=self)
 
-    @property
-    def availabilities_total_duration(self):
-        from AKModel.availability.models import Availability
-        for a in Availability.objects.filter(ak=self):
-            print(a)
-            print(a.end)
-            #        [a.end - a.start for a in ]
-        return 0
 
 class Room(models.Model):
     """ A room describes where an AK can be held.