Use ModelList for tests

[VEZY]

Atm I use a mapping for testing simple models, but we should be able to run them using a ModelList instead. This is not possible right now for models that use a value from the previous time-step because we don't have the same behavior between mapping (same status updated each time-step) and ModelList (independent status for each time-step). This will be possible when VirtualPlantLab/PlantSimEngine.jl#101 is closed.