Redesign URL rewrite framework for sophisticated rewrite

[kngenie]

such as:

• maintaining the form of URL (absolute, protocol-relative, server-relative, path-relative) - to make it less likely to break when manipulated by JavaScript.
• changing protocol depending on X-Forwarded-Proto request header field - important for deployment with reverse-proxy.

These are very hard to implement with current framework.

Details on current work at IA: https://github.com/internetarchive/wayback/issues/53