Remove confidence bands option using cal_plot_multi

[drjgauthier]

Things get a little crowded when comparing multiple models.
For example:

It would be very helpful to have the option to hide the confidence bands. Just a thought! ;)

[kdpsingh]

I agree we should provide this option, particularly for any of the multi-model plots where the overlapping confidence bands can get really busy. The default will still be to display the confidence intervals.

[kdpsingh]

Also, recognizing that journals often charge for color figures, we should consider showing different models as different line types (eg dotted, dashed) if the confidence intervals don't need to be plotted.