Introduce detail and edit URLs as properties in AK model

• This way, the frontend views will be used when AKSubmission is installed and active, or otherwise the link to the built-in AK edit form in backend
• This reduces the coupling between AKSubmission and other apps that previously needed that app
• Use that new property in all places where previously an URL to the submission view was used (for consistency and to allow changes in one place in AKSubmission, too)
• This implements #166 (closed)

AKModel/models.py

@@ -329,13 +329,13 @@ class AK(models.Model):
 
     @property
     def edit_url(self):
-        if apps.is_installed("AKScheduling"):
+        if apps.is_installed("AKSubmission"):
             return reverse_lazy('submit:ak_edit', kwargs={'event_slug': self.event.slug, 'pk': self.id})
         return reverse_lazy('admin:AKModel_ak_change', kwargs={'object_id': self.id})
 
     @property
     def detail_url(self):
-        if apps.is_installed("AKScheduling"):
+        if apps.is_installed("AKSubmission"):
             return reverse_lazy('submit:ak_detail', kwargs={'event_slug': self.event.slug, 'pk': self.id})
         return self.edit_url