Merge parameters in strict mode

[ivborissov]

Current setup allows adding new parameters at Scenario level with @warn warning the user, that the parameter is missing in the model.
Is that the intended behavior ? Potentially it may cause misprints.

An idea is to set strict=true kwarg and change the default behavior to throwing an error in case the provided parameter is missing in the model. If the user is sure about this new parameter he can change strict=false.