[MPI] Centralize Logging

[csegarragonz]

Aggregate all different log files created by MPI processes to enhance debugging.

[Shillaker]

As mentioned in the review, remember that this MPI stuff is meant to be a prototype for experimentation, so we don't want to spend too much engineering time on it. Simple aggregation of logs from containers run by docker-compose should be possible with docker-compose logs too.