Feature request: Hooks/Signals in Karton

Hey!

Similar to the plugin system in MWDB, it would be nice to have a hook system implemented in Karton.
It could expose the following callbacks:
- on_task_started
- on_task_crashed
- on_task_timeout
- on_analysis_finished
and so on.

I think that the plugins directory in MWDB where you can define some plugin class is a good and simple design that might fit in karton too