Multiscale mapping to other variable name

[VEZY]

Make it possible to map a set of variables from different scales into a scale, but with a different variable name. For example, if we want to take the value of Rm in the organs and pass the vector as input of Rm_organs we would do:

MultiScaleModel(
	model=PlantRm(),
	mapping=[:Rm => ["Leaf", "Internode", "Male", "Female"] => :Rm_organs],
)

This allows to put Rm as output of our model, instead of having to rename it.

Before we had to have this kind of models:

struct PlantRm <: AbstractMaintenance_RespirationModel end

PlantSimEngine.inputs_(::PlantRm) = (Rm=[-Inf],)
PlantSimEngine.outputs_(::PlantRm) = (Rm_plant=-Inf,)

function PlantSimEngine.run!(::PlantRm, models, status, meteo, constants, extra=nothing)
    status.Rm_plant = sum(status.Rm)
end

With this feature we could say that the input Rm from other scales takes another name, so we can use Rm for the output at this scale:

struct PlantRm <: AbstractMaintenance_RespirationModel end

PlantSimEngine.inputs_(::PlantRm) = (Rm_organs=[-Inf],)
PlantSimEngine.outputs_(::PlantRm) = (Rm=-Inf,)

function PlantSimEngine.run!(::PlantRm, models, status, meteo, constants, extra=nothing)
    status.Rm = sum(status.Rm_organs)
end

This is much more consistent and allows to keep the same variable names across scales, e.g. Rm is the respiration maintenance of the given scale, whatever the scale.

[VEZY]

I read the code quickly, and I think we could do that for MappedVar by setting the var field to the variable that we get from other scales, and the var we put this into as the var we want to put it in, e.g.:

Rm_organs = MappedVar(["Leaf", "Internode", "Male", "Female"], :Rm, [-Inf])

For RefVector, I'm not sure yet. We could add a var field too, but it would stay there in the status then. I don't know if that's good or bad.

[VEZY]

Closed in the latest work I did in the past couple of weeks. This was not done in a PR unfortunately (this has to change!).