Support for plotting MultiParameter data

[NicoHendrickx]

I have trouble plotting data that was measured as a MultiParameter in qcodes. This results in the different traces having their own setpoints, rather than sharing the same setpoint array (as is the case for multiple measurement parameters).

This seems to lead to a number of issues in plottr-inspectr, as it seems to expect the same setpoints for all datasets.

I understand that the traces can thus not be plotted in the same plot, but also when selecting individual traces mode, it is not possible to select more than one of the data sets (the other is greyed out).

Furthermore, when deselecting one data set, and selecting any but the first from the MultiParameter, the Role of the setpoints is set to None, resulting in not plotting the data. One has to manually select 'x-axis' again to view the data. This is accompanied by a warning in the log: plottr.node.dim_reducer.XYSelector.Dimension assignment - WARNING x-Axis <setpoints_of_dataset0> not present in data where <setpoints_of_dataset0> is the name of the setpoints of the first parameter/dataset.

Thanks in advance!