Configure screenshot service

[vollstock]

Additionall to switching the service on and of, we could also configure other things:

• thumbnail size
• png <-> jpg
• quality
• days after which screenshots get deleted
• days after which thumbnails get deleted

I assume, we shouldn't present all of these options but make good defaults. Let’s not blow up the UI.

To change these, we need to adjust the cronjob and/or screenshot script.
The script is here /opt/tooloop/scripts/tooloop-screenshot

[vollstock]

I had an instance, where the harddrive was very small and the 4K screenshots were big.
At some point there wasn't enough space on the harddrive and the system wouldn’t run properly.

Some configuration would maybe have helped.