MeanModel/PopWorkflow: split "REsiduals over all simulations" plots by output

[Yuri05]

At the moment we have just 1 plot for all outputs and all simulation sets.
This plot should be splitted by Output into N plots (this applies to all plot types in the section "Residuals across all simulations")

Todo: here we have the same output for N simulations in the same plot, so that the colouring schema defined per Output (#883) cannot be applied.
So in these plots the colour must be unique not for the output but for the simulationset