Show methods for Style Objects Should Be Improved

[brodieG]

Right now there is branching logic within the show-style method based on whether the style is an ansi style or not, when ideally this would be handled via S4 dispatch if possible. Additionally, StyleHtml do not display to browser. One tension to resolve here is whether the show-Style methods should be exclusively for the terminal, particularly because they are used by show-PaletteOfStyles and mixed outputs will not work well.

One other reason to address this is that users could potentially define new styles (e.g. grid graphics) and this seems to be one of the places that assumes styles are either ANSI or html.