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
* Split response size into normal responses and AXFR|IXFR responses.
* Split out incoming sizes as well in normal and AXFR|IXFRs.
* Add meta qtype to the monitored qtypes.
* Make duration to be exported in milliseconds instead of seconds.
