Add configs for path to write and read wacz archives

[liliakai]

To support running browstrix in docker while also running the auto-archiver(api) in docker, we add separate configs for where browsertrix writes the archives and where the wacz enricher reads the archives, because one is relative to the host and one is relative to the container, even though they may refer to the same volume.

[liliakai]

Perhpas these configs should be environment variables instead, so one could set them directly from a docker compose file, reducing the amount of configuration needed. What do you think @msramalho ?

[msramalho]

Although I'm wary of using both env and configs, since these are only used when running in docker I think env variables make sense, perhaps we could later on have a docker-compose with everything setup (volumes and env vars).