simulation: add event-based simulation

doc/references.bib

src/simulation/clock.py

src/simulation/closed_loop.py

src/simulation/disturbance.py

src/simulation/signal.py

src/simulation/state_abstraction.py

src/simulation/switching_sequence.py

src/simulation/system_model.py

src/test/simulation/clock/__init__.py

src/test/simulation/clock/constructor.py

src/test/simulation/clock/wait_for_tick.py

src/test/simulation/closed_loop/__init__.py

src/test/simulation/closed_loop/constructor_wrappers.py

src/test/simulation/closed_loop/simulate.py

src/test/simulation/disturbance/__init__.py

src/test/simulation/disturbance/constructor.py

src/test/simulation/disturbance/process.py

src/test/simulation/switching_sequence/__init__.py

src/test/simulation/switching_sequence/constructor.py

...tion/switching_sequence/mk_switching_sequence/__init__.py