Holoviews: Document how to control legends

[philippjfr]

The Styling Plots user guide provides a guide on styling plots currently focused on colors, cycles and colormaps. It would be good to also add a section on controlling legends.

[Bonnevie]

This would be great. At the moment the only support for legends I have been able to find is the legend_example in the gallery, and proper legends is fairly important for most figures.

[neighthan]

I would especially like to know how to force a legend to be shown. For example, if I plot multiple curves as an overlay, a legend is shown by default, but I don't know how to show a legend for just a single curve. I've tried using the show_legend option, but this doesn't work:

import holoviews as hv
hv.extension("matplotlib")

hv.Curve([1,2,3], label="label").opts(show_legend=True)