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/hosts/setup.go

@@ -0,0 +1,88 @@
+package hosts
+
+import (
+	"log"
+	"os"
+	"path"
+
+	"github.com/coredns/coredns/core/dnsserver"
+	"github.com/coredns/coredns/plugin"
+
+	"github.com/mholt/caddy"
+)
+
+func init() {
+	caddy.RegisterPlugin("hosts", caddy.Plugin{
+		ServerType: "dns",
+		Action:     setup,
+	})
+}
+
+func setup(c *caddy.Controller) error {
+	h, err := hostsParse(c)
+	if err != nil {
+		return plugin.Error("hosts", err)
+	}
+
+	dnsserver.GetConfig(c).AddPlugin(func(next plugin.Handler) plugin.Handler {
+		h.Next = next
+		return h
+	})
+
+	return nil
+}
+
+func hostsParse(c *caddy.Controller) (Hosts, error) {
+	var h = Hosts{
+		Hostsfile: &Hostsfile{path: "/etc/hosts"},
+	}
+	defer h.ReadHosts()
+
+	config := dnsserver.GetConfig(c)
+
+	for c.Next() {
+		args := c.RemainingArgs()
+		if len(args) >= 1 {
+			h.path = args[0]
+			args = args[1:]
+
+			if !path.IsAbs(h.path) && config.Root != "" {
+				h.path = path.Join(config.Root, h.path)
+			}
+			_, err := os.Stat(h.path)
+			if err != nil {
+				if os.IsNotExist(err) {
+					log.Printf("[WARNING] File does not exist: %s", h.path)
+				} else {
+					return h, c.Errf("unable to access hosts file '%s': %v", h.path, err)
+				}
+			}
+		}
+
+		origins := make([]string, len(c.ServerBlockKeys))
+		copy(origins, c.ServerBlockKeys)
+		if len(args) > 0 {
+			origins = args
+		}
+
+		for i := range origins {
+			origins[i] = plugin.Host(origins[i]).Normalize()
+		}
+		h.Origins = origins
+
+		for c.NextBlock() {
+			switch c.Val() {
+			case "fallthrough":
+				args := c.RemainingArgs()
+				if len(args) == 0 {
+					h.Fallthrough = true
+					continue
+				}
+				return h, c.ArgErr()
+			default:
+				return h, c.Errf("unknown property '%s'", c.Val())
+			}
+		}
+	}
+	return h, nil
+}