Remove the word middleware (#1067)

* Rename middleware to plugin

first pass; mostly used 'sed', few spots where I manually changed
text.

This still builds a coredns binary.

* fmt error

* Rename AddMiddleware to AddPlugin

* Readd AddMiddleware to remain backwards compat

plugin/dnstap/setup_test.go

@@ -0,0 +1,34 @@
+package dnstap
+
+import (
+	"github.com/mholt/caddy"
+	"testing"
+)
+
+func TestConfig(t *testing.T) {
+	tests := []struct {
+		file   string
+		path   string
+		full   bool
+		socket bool
+		fail   bool
+	}{
+		{"dnstap dnstap.sock full", "dnstap.sock", true, true, false},
+		{"dnstap unix://dnstap.sock", "dnstap.sock", false, true, false},
+		{"dnstap tcp://127.0.0.1:6000", "127.0.0.1:6000", false, false, false},
+		{"dnstap", "fail", false, true, true},
+	}
+	for _, c := range tests {
+		cad := caddy.NewTestController("dns", c.file)
+		conf, err := parseConfig(&cad.Dispenser)
+		if c.fail {
+			if err == nil {
+				t.Errorf("%s: %s", c.file, err)
+			}
+		} else if err != nil || conf.target != c.path ||
+			conf.full != c.full || conf.socket != c.socket {
+
+			t.Errorf("expected: %+v\nhave: %+v\nerror: %s\n", c, conf, err)
+		}
+	}
+}