add custom cron file to nextcloud image #78

Job	Run time
Build App Containers (minecraft) / Build minecraft	16s
Build App Containers (etherpad) / Build etherpad	40s
Build App Containers (limesurvey) / Build limesurvey	38s
Build App Containers (indico) / Build indico	2m 16s
Build App Containers (nextcloud) / Build nextcloud	1m 35s
Build App Containers (sogo) / Build sogo	3m 12s
	8m 37s

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