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/pprof/setup.go

@@ -0,0 +1,53 @@
+package pprof
+
+import (
+	"net"
+	"sync"
+
+	"github.com/coredns/coredns/plugin"
+
+	"github.com/mholt/caddy"
+)
+
+const defaultAddr = "localhost:6053"
+
+func init() {
+	caddy.RegisterPlugin("pprof", caddy.Plugin{
+		ServerType: "dns",
+		Action:     setup,
+	})
+}
+
+func setup(c *caddy.Controller) error {
+	found := false
+	h := &handler{addr: defaultAddr}
+	for c.Next() {
+		if found {
+			return plugin.Error("pprof", c.Err("pprof can only be specified once"))
+		}
+		args := c.RemainingArgs()
+		if len(args) == 1 {
+			h.addr = args[0]
+			_, _, e := net.SplitHostPort(h.addr)
+			if e != nil {
+				return e
+			}
+		}
+		if len(args) > 1 {
+			return plugin.Error("pprof", c.ArgErr())
+		}
+		if c.NextBlock() {
+			return plugin.Error("pprof", c.ArgErr())
+		}
+		found = true
+	}
+
+	pprofOnce.Do(func() {
+		c.OnStartup(h.Startup)
+		c.OnShutdown(h.Shutdown)
+	})
+
+	return nil
+}
+
+var pprofOnce sync.Once