add cronjob

cron.py

@@ -0,0 +1,18 @@
+# -*- coding: utf-8 -*-
+# This file is part of the cashbook-planner from m-ds for Tryton.
+# The COPYRIGHT file at the top level of this repository contains the
+# full copyright notices and license terms.
+
+from trytond.pool import PoolMeta
+
+
+class Cron(metaclass=PoolMeta):
+    __name__ = 'ir.cron'
+
+    @classmethod
+    def __setup__(cls):
+        super(Cron, cls).__setup__()
+        cls.method.selection.append(
+            ('cashbook.planner|cronjob', "Execute scheduled bookings"))
+
+# end Cron