Make CoreDNS a server type plugin for Caddy (#220)

* Make CoreDNS a server type plugin for Caddy

Remove code we don't need and port all middleware over. Fix all tests
and rework the documentation.

Also make `go generate` build a caddy binary which we then copy into
our directory. This means `go build`-builds remain working as-is.

And new etc instances in each etcd test for better isolation.
Fix more tests and rework test.Server with the newer support Caddy offers.

Fix Makefile to support new mode of operation.

middleware/dnssec/setup_test.go

@@ -0,0 +1,56 @@
+package dnssec
+
+import (
+	"strings"
+	"testing"
+
+	"github.com/mholt/caddy"
+)
+
+func TestSetupDnssec(t *testing.T) {
+	tests := []struct {
+		input              string
+		shouldErr          bool
+		expectedZones      []string
+		expectedKeys       []string
+		expectedErrContent string
+	}{
+		{
+			`dnssec`, false, nil, nil, "",
+		},
+		{
+			`dnssec miek.nl`, false, []string{"miek.nl."}, nil, "",
+		},
+	}
+
+	for i, test := range tests {
+		c := caddy.NewTestController("dns", test.input)
+		zones, keys, err := dnssecParse(c)
+
+		if test.shouldErr && err == nil {
+			t.Errorf("Test %d: Expected error but found %s for input %s", i, err, test.input)
+		}
+
+		if err != nil {
+			if !test.shouldErr {
+				t.Errorf("Test %d: Expected no error but found one for input %s. Error was: %v", i, test.input, err)
+			}
+
+			if !strings.Contains(err.Error(), test.expectedErrContent) {
+				t.Errorf("Test %d: Expected error to contain: %v, found error: %v, input: %s", i, test.expectedErrContent, err, test.input)
+			}
+		}
+		if !test.shouldErr {
+			for i, z := range test.expectedZones {
+				if zones[i] != z {
+					t.Errorf("Dnssec not correctly set for input %s. Expected: %s, actual: %s", test.input, z, zones[i])
+				}
+			}
+			for i, k := range test.expectedKeys {
+				if k != keys[i].K.Header().Name {
+					t.Errorf("Dnssec not correctly set for input %s. Expected: '%s', actual: '%s'", test.input, k, keys[i].K.Header().Name)
+				}
+			}
+		}
+	}
+}