Use logging.

Replaced all print() calls with logger.info/debug. Printing evidence objects. Logging to /var/log/evidence_collector.log and setting tailf to this file in docker entrypoint.
Version 0.0.4.

Squashed commit of the following:

commit 825d1f95a141f8e11703c27889e53a6e16c3cd66
Author: Anže Žitnik <anze.zitnik@xlab.si>
Date:   Wed Dec 1 12:21:26 2021 +0100

    Output logs to /var/log... and tailf in Dockerfile

commit db9b34317d19e42316fc0c5f0a8f60b03b2e4dbc
Author: Anže Žitnik <anze.zitnik@xlab.si>
Date:   Wed Dec 1 12:19:54 2021 +0100

    Introduce logger. Replace all prints.