Created a class `BaseAgent`, from which all agents inherit. They get
assigned a logger with a nice name (something like
`control_backend.agents.AgentName`).
The BDI core takes care of its own logger, as bdi is still a module.
ref: N25B-241
Add a custom logging setup function to add custom levels and custom
formatters (partly for future use with extended logging functionality).
Also implemented a basic colored formatter to make our logs nicer.
Also improved the handling of logging in external libraries, so now we
should only get WARNings or above.
ref: N25B-233
