Colormaps support giving colors for bad, under and over values on creation

Colormaps gained keyword arguments bad, under, and over to specify these values on creation. Previously, these values would have to be set afterwards using one of set_bad, set_under, set_bad, set_extremes, with_extremes.

It is recommended to use the new functionality, e.g.:

cmap = ListedColormap(colors, bad="red", under="darkblue", over="purple")

instead of:

cmap = ListedColormap(colors).with_extremes(
    bad="red", under="darkblue", over="purple")

or:

cmap = ListedColormap(colors)
cmap.set_bad("red")
cmap.set_under("darkblue")
cmap.set_over("purple")