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/trace/setup_test.go

@@ -0,0 +1,60 @@
+package trace
+
+import (
+	"testing"
+
+	"github.com/mholt/caddy"
+)
+
+func TestTraceParse(t *testing.T) {
+	tests := []struct {
+		input        string
+		shouldErr    bool
+		endpoint     string
+		every        uint64
+		serviceName  string
+		clientServer bool
+	}{
+		// oks
+		{`trace`, false, "http://localhost:9411/api/v1/spans", 1, `coredns`, false},
+		{`trace localhost:1234`, false, "http://localhost:1234/api/v1/spans", 1, `coredns`, false},
+		{`trace http://localhost:1234/somewhere/else`, false, "http://localhost:1234/somewhere/else", 1, `coredns`, false},
+		{`trace zipkin localhost:1234`, false, "http://localhost:1234/api/v1/spans", 1, `coredns`, false},
+		{`trace zipkin http://localhost:1234/somewhere/else`, false, "http://localhost:1234/somewhere/else", 1, `coredns`, false},
+		{"trace {\n every 100\n}", false, "http://localhost:9411/api/v1/spans", 100, `coredns`, false},
+		{"trace {\n every 100\n service foobar\nclient_server\n}", false, "http://localhost:9411/api/v1/spans", 100, `foobar`, true},
+		{"trace {\n every 2\n client_server true\n}", false, "http://localhost:9411/api/v1/spans", 2, `coredns`, true},
+		{"trace {\n client_server false\n}", false, "http://localhost:9411/api/v1/spans", 1, `coredns`, false},
+		// fails
+		{`trace footype localhost:4321`, true, "", 1, "", false},
+		{"trace {\n every 2\n client_server junk\n}", true, "", 1, "", false},
+	}
+	for i, test := range tests {
+		c := caddy.NewTestController("dns", test.input)
+		m, err := traceParse(c)
+		if test.shouldErr && err == nil {
+			t.Errorf("Test %v: Expected error but found nil", i)
+			continue
+		} else if !test.shouldErr && err != nil {
+			t.Errorf("Test %v: Expected no error but found error: %v", i, err)
+			continue
+		}
+
+		if test.shouldErr {
+			continue
+		}
+
+		if test.endpoint != m.Endpoint {
+			t.Errorf("Test %v: Expected endpoint %s but found: %s", i, test.endpoint, m.Endpoint)
+		}
+		if test.every != m.every {
+			t.Errorf("Test %v: Expected every %d but found: %d", i, test.every, m.every)
+		}
+		if test.serviceName != m.serviceName {
+			t.Errorf("Test %v: Expected service name %s but found: %s", i, test.serviceName, m.serviceName)
+		}
+		if test.clientServer != m.clientServer {
+			t.Errorf("Test %v: Expected client_server %t but found: %t", i, test.clientServer, m.clientServer)
+		}
+	}
+}