Added a little batch command that removes all unnecessary DB rows on a schedule (each day)

We have been removing registered visits from the start, and added unused stats a few days ago. Now all other things considered temporary are automatically removed every day instead of after 14 days (like visits).

Enabling our customers visitors to check-in by sending a WhatsApp message caused us to integrate some sort of logging; otherwise we couldn't possible know in which stage of the check-in people were. We don't like logging and we don't like useless data; everything gets removed within 24 hours now.