middleware/file: add DNSSEC support (#697)

* middleware/file: add DNSSEC support

Add tests for DNSSEC and check if everything is working.

* add signatures

* tweak

* Add DNSSEC signing tests for DNAME

* Just sign it all

middleware/dnssec/dnssec.go

@@ -43,6 +43,7 @@ func (d Dnssec) Sign(state request.Request, zone string, now time.Time) *dns.Msg
 
 	mt, _ := response.Typify(req, time.Now().UTC()) // TODO(miek): need opt record here?
 	if mt == response.Delegation {
+		// TODO(miek): uh, signing DS record?!?!
 		return req
 	}