NF,DOC improve docstring for show and make_static

[mvdoc]

This PR

• reorganizes the order of the kwargs for both cortex.webgl.view.show and cortex.webgl.view.make_static so that they match the docstring
• improves the docstring for both functions
• allows passing curvature_{brightness,contrast,curvature} to make_static too
• adds a new keyword surface_specularity in both functions to allow disabling that hideous surface specularity 😝
• removes the cmap kwarg since it doesn't do anything anymore