Callback machine

[guillain]

creation + added in input and menu machines

Done:

• test validation (367)
• scenario validation

ToDo:

• specific tests to add
• example to update/create

[bernard357]

Interesting contribution, thanks for it. We had some issue with bare callbacks in the past because of the deletion of references. For this reason, a similar mechanism has been implemented in bot.py itself. You can look for dispatch() there if you like. Would you be ok if I work on some extension of existing code in bot.py ? This could save on the introduction of a separate observable.py

[guillain]

Thanks