merge the current development branch into master

[andreashappe]

This is the initial merge. There will be at least another merge-requests containing smaller features as well as cleanups before we will release 0.3.

The big thing here is:

• cleanup the usecase vs. agent hierarchy: before this, use-cases and agents were part of the same class hierarchy. Now we have agents that describe what an exploitation agent is doing. They are separated from use-cases that use the agents and provide configuration and logging infrastructure.

The documentation at docs.hackingbuddy.ai already reflects this change.