Remove the render-html module

[carltonwhitehead]

render-html caters to single-file, self-contained, static HTML reports. I don't want to use these in the long term, preferring a competition web app (think live timing) with an embedded web server.

Not all effort on the render-html module is wasted. Quite a lot of the kotlinx-html based renderers should be useful. Do this removal after implementing the results web app / server.