HistoryMatch: Misfit improvements

[HansKallekleiv]

Future frontend/Dash component improvements include:

• Add a "guided tour" to the plugin (as already added for some other plugins), explaining the user what he/she is looking at (especially the confidence intervals in the background, indicating areas of overfitting/underfitting, might be a difficult concept).
• Move legend out of the plot. Visualize axis ticks better on small screens.
• Option for showing total misfit per group (i.e. contribution in the misfit function), and not only average misfit within a group (as now).
• Observation type aggregation (currently it is one bar per "obs. group/key", e.g. WOPR:A-1H... would perhaps be useful to easily be able to aggregate this such that you show average/total normalized misfit for WOPR:* as a total, and Rates (WOPR, WGPR, WWPR etc.) as a even higher aggregration level).
• When hovering over a misfit bar, it could "dissolve" into the different "realization points" (a technique also used in the Parameter Distribution Plugin) - enabling the user to easily identify realizations with good/bad match wrt. to a given observation type.