Add a line to the top panel of the state plot that indicates the max-min likelihood difference

[cchapmanbird]

Is your feature request related to a problem? Please describe. While it is useful to track how the maximum/minimum likelihood are changing with time during a run, large scale differences can lead to the two lines lying on top of each other which is not informative.

Describe the solution you'd like Modify the top panel of the state plot to also produce a line that plots the difference between the maximum and minimum log-likelihood against a (log-scaled) y axis on the right-hand side