Fixed #107 and fixed #125 -- Periodic cleanup tasks

src/pretix/base/management/commands/runperiodic.py

@@ -0,0 +1,12 @@
+from django.core.management import call_command
+from django.core.management.base import BaseCommand
+
+from ...signals import periodic_task
+
+
+class Command(BaseCommand):
+    help = "Run periodic tasks"
+
+    def handle(self, *args, **options):
+        periodic_task.send(self)
+        call_command('clearsessions')