feature: restart recording on raspicams

[walachey]

We had odd recording issues (no heartbeat file written) on the raspicams that were resolved by simply restarting the bb_raspicam service.

The bb_monitor script should try straight-forward fixes directly after identifying certain issues.

• Potentially, it could run these fixes only on the hourly checks so that it does not interfere with people accessing the device physically?
• The raspi acquisition systemd service should ideally be set to restart automatically and always
• When no heartbeat file is found for the raspis, the monitor script should just kill all image acquisition processes (by name)
• (and then systemd would restart it)