CDK-751: Add Kite start page as index.html.

This includes Dennis's edits from CDK-751.

The existing index has been moved to all-pages.md. This needs to be
improved before committing, possibly by organizing all pages and adding
a sidebar rather than using all-pages directly.

This is a subset of the changes from the original proposed branch, which I'm breaking up into multiple pull requests. this one just includes the front page changes and updates to the style to replace the old side, like adding footer links to the issue tracker and github.