Move all (almost all) Go files in middleware into their
own packages. This makes for better naming and discoverability.
Lot of changes elsewhere to make this change.
The middleware.State was renamed to request.Request which is better,
but still does not cover all use-cases. It was also moved out middleware
because it is used by `dnsserver` as well.
A pkg/dnsutil packages was added for shared, handy, dns util functions.
All normalize functions are now put in normalize.go
Make the CH middleware actually work. Needs a bit of a hack to route
the fake version.bind and friends zone to the correct handler. Fiddle
with the order in directive.go so that CH queries get logged as well.
Secondly add class rewriting to the rewrite middleware handler and also
log the class by default.
