Skeleton router

First fruits from the skeleton + policies approach (OPTIONS * largely implemented).
Frozen routines with policy hooks are used to further enforce (in addition to contracts) HTTP compliance.

I haven't yet worked out the policy for HTTP/1.0 support (i.e. sending 305 Use proxy responses) should come in. Probably very early on. My preference is to code purely for HTTP/1.1, and always require HTTP/1.0 clients to use a proxy. This makes coding the skeleton framework plausible. But if anyone wants to support HTTP/1.0 clients without using a proxy, then we need an alternative strategy (e.g. not using the skeleton + policies approach).

I propose only to implement the full skeleton for just the URI template router, as it should be the only one needed (I think it subsumes the others?), and otherwise we need to duplicate too much code.