Improve hooks system

[Devatoria]

It would be cool to have a more complete hooks system with some features like:

• a SetupHook function called on hook registration and used to initialize the hook
• allow hook to have hook-specific fields in the structure (private) to store some values across the hook lifecycle

It could probably be done using interface and composition systems, but it also needs to review a lot of things (tests, hook manager, ...). To be discussed.