Passing the event as parameter of an action

[pdeligia]

We should pass the event that triggered an action as the parameter to this action. The user will then declare (for example):

on SomeEvent do SomeAction;
SomeAction(SomeEvent e) { ... }

We should check (dynamically for now, but later on statically) that the action is indeed accepting the expected event as a parameter. We can then get rid of this.ReceivedEvent (and the corresponding rewriting).

This will simplify stuff. In the future, we could think how to pass the actual payload of the event as parameters (but this might be more expensive to do).