Readable AK times on details page

Before:

Dauer	Wann?	Raum
1,50	Sun 23:00	Internet

After:

Wann?	Dauer	Raum
Sun 23:00 - Mon 00:30	1:30	Internet

AKModel/models.py

@@ -345,6 +345,15 @@ class AKSlot(models.Model):
             return _("Not scheduled yet")
         return self.start.astimezone(self.event.timezone).strftime('%a %H:%M')
 
+    @property
+    def time_simplified(self):
+        """
+        Display start and end time of slot in format weekday + time, e.g. "Fri 14:00 - 15:30"
+        """
+        if self.start is None:
+            return _("Not scheduled yet")
+        return self.start.astimezone(self.event.timezone).strftime('%a %H:%M') + ' - ' + self.end.astimezone(self.event.timezone).strftime('%H:%M')
+
     @property
     def end(self):
         """