Make `DistributionPlot` use parameters

[rubenthoms]

[anders-kiaer]

The main use cases here:

Parameter vs reponse:

Plotting parameter value versus other response values (like simulation time series), mapped by realization index.

See https://webviz-subsurface-example.azurewebsites.net/parameter-analysis (page "Parameter Response Analysis"). Good candicate for a new template using the template system?

Parameter vs parameter:

Plotting parameter value versus parameter value, also this one mapped by realization index.
See https://webviz-subsurface-example.azurewebsites.net/parameters-vs-parameters