Use logging (#1718)

* update docs

* plugins: use plugin specific logging

Hooking up pkg/log also changed NewWithPlugin to just take a string
instead of a plugin.Handler as that is more flexible and for instance
the Root "plugin" doesn't implement it fully.

Same logging from the reload plugin:

.:1043
2018/04/22 08:56:37 [INFO] CoreDNS-1.1.1
2018/04/22 08:56:37 [INFO] linux/amd64, go1.10.1,
CoreDNS-1.1.1
linux/amd64, go1.10.1,
2018/04/22 08:56:37 [INFO] plugin/reload: Running configuration MD5 = ec4c9c55cd19759ea1c46b8c45742b06
2018/04/22 08:56:54 [INFO] Reloading
2018/04/22 08:56:54 [INFO] plugin/reload: Running configuration MD5 = 9e2bfdd85bdc9cceb740ba9c80f34c1a
2018/04/22 08:56:54 [INFO] Reloading complete

* update docs

* better doc

plugin/etcd/setup.go

@@ -6,6 +6,7 @@ import (
 
 	"github.com/coredns/coredns/core/dnsserver"
 	"github.com/coredns/coredns/plugin"
+	clog "github.com/coredns/coredns/plugin/pkg/log"
 	mwtls "github.com/coredns/coredns/plugin/pkg/tls"
 	"github.com/coredns/coredns/plugin/pkg/upstream"
 	"github.com/coredns/coredns/plugin/proxy"
@@ -14,6 +15,8 @@ import (
 	"github.com/mholt/caddy"
 )
 
+var log = clog.NewWithPlugin("etcd")
+
 func init() {
 	caddy.RegisterPlugin("etcd", caddy.Plugin{
 		ServerType: "dns",

plugin/etcd/stub.go

@@ -7,7 +7,6 @@ import (
 
 	"github.com/coredns/coredns/plugin/etcd/msg"
 	"github.com/coredns/coredns/plugin/pkg/dnsutil"
-	"github.com/coredns/coredns/plugin/pkg/log"
 	"github.com/coredns/coredns/plugin/proxy"
 	"github.com/coredns/coredns/request"
 

plugin/etcd/stub_handler.go

@@ -4,7 +4,6 @@ import (
 	"context"
 	"errors"
 
-	"github.com/coredns/coredns/plugin/pkg/log"
 	"github.com/coredns/coredns/request"
 
 	"github.com/miekg/dns"