Improve on logging and stderr'ing stuff

[paulo-ferraz-oliveira]

Is your feature request related to a problem?

Not really, more like a maintenance issue.

Describe the feature you'd like

I'd like there to be log functions (for both the log file and stderr, and similar) so we wouldn't keep appending to a file here and there, for example. This surfaced as an idea during the implementation of #471.

Describe alternatives you've considered

Not changing the code 😄