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/secondary/setup_test.go

@@ -0,0 +1,65 @@
+package secondary
+
+import (
+	"testing"
+
+	"github.com/mholt/caddy"
+)
+
+func TestSecondaryParse(t *testing.T) {
+	tests := []struct {
+		inputFileRules string
+		shouldErr      bool
+		transferFrom   string
+		zones          []string
+	}{
+		{
+			`secondary`,
+			false, // TODO(miek): should actually be true, because without transfer lines this does not make sense
+			"",
+			nil,
+		},
+		{
+			`secondary {
+				transfer from 127.0.0.1
+				transfer to 127.0.0.1
+			}`,
+			false,
+			"127.0.0.1:53",
+			nil,
+		},
+		{
+			`secondary example.org {
+				transfer from 127.0.0.1
+				transfer to 127.0.0.1
+			}`,
+			false,
+			"127.0.0.1:53",
+			[]string{"example.org."},
+		},
+	}
+
+	for i, test := range tests {
+		c := caddy.NewTestController("dns", test.inputFileRules)
+		s, err := secondaryParse(c)
+
+		if err == nil && test.shouldErr {
+			t.Fatalf("Test %d expected errors, but got no error", i)
+		} else if err != nil && !test.shouldErr {
+			t.Fatalf("Test %d expected no errors, but got '%v'", i, err)
+		}
+
+		for i, name := range test.zones {
+			if x := s.Names[i]; x != name {
+				t.Fatalf("Test %d zone names don't match expected %q, but got %q", i, name, x)
+			}
+		}
+
+		// This is only set *iff* we have a zone (i.e. not in all tests above)
+		for _, v := range s.Z {
+			if x := v.TransferFrom[0]; x != test.transferFrom {
+				t.Fatalf("Test %d transform from names don't match expected %q, but got %q", i, test.transferFrom, x)
+			}
+		}
+	}
+}