Allow usage as library

[andreashappe]

Currently all agents are defined within usecases which is great for the initial phase of our projects (where most contributors are adding new agents). In the long run, it would be better to allow 'external' agents that are stored outside of the project directory.

In such a case, hackingbuddyGPT would be installed through pip and pointed to the agent definition to execute the agent.

[andreashappe]

the version in the current restructure branch is already install-able through pip.

Before I push this onto pypi, I'll have to add some additional "things":

• some sort of warning, that you only should use this with test-systems
• update the documentation