Allow user provided probe hooks

[atenart]

Allow the user to provide its own BPF object file and load it as a hook in the probes. For this to work the following topics needs to be covered:

• Provide a way to compile BPF objects using our interfaces and specific data.
• Allow loading external objects.
• Having generic logic to fill events with generic data and to retrieve it.

[atenart]

Fixed in #22 .