Fix #1509 - Add cron task for deleting batch results (#1525) #1457

Job	Run time
build-docker (internet.nl, docker/Dockerfile, app)	1m 23s
build-docker (unbound, docker/Dockerfile, unbound)	56s
build-docker (linttest, docker/Dockerfile, linttest)	1m 15s
build-docker (test-runner, docker/test-runner.Dockerfile)	1m 20s
build-docker (webserver, docker/webserver.Dockerfile)	57s
build-docker (grafana, docker/grafana.Dockerfile)	1m 9s
build-docker (cron, docker/cron.Dockerfile)	1m 20s
integration-test	3m 17s
lint/check	41s
docs	1s
development-environment-test	2m 36s
batch-integration-test	2m 34s
test	2m 24s
	19m 53s

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