Refactoring
Minot modif that concerns the activation of interactors
- change: Should use the interfaces Instrument, Interactor, and
Interaction instead of their implementation class when possible.
  So, the classes Instrument, Interactor, and Interaction have been
renamed as InstrumentImpl, InteractorImpl, and InteractionImpl.
- change: API renaming: State, Transition -> StateImpl, TransitionImpl;
IState, ITransition, IStateMachine -> State, Transition, StateMachine.