config/main: Re-write config files - add to new config v3

- New config format.

```
{
	"version": "3",
	"address": ":9000",
    "backend": {
          "type": "fs",
          "disk": "/path"
    },
	"credential": {
		"accessKey": "WLGDGYAQYIGI833EV05A",
		"secretKey": "BYvgJM101sHngl2uzjXS/OBF/aMxAN06JrJ3qJlF"
	},
	"region": "us-east-1",
	"logger": {
		"file": {
			"enable": false,
			"fileName": "",
			"level": "error"
		},
		"syslog": {
			"enable": false,
			"address": "",
			"level": "debug"
		},
		"console": {
			"enable": true,
			"level": "fatal"
		}
	}
}
```

New command lines in lieu of supporting XL.

Minio initialize filesystem backend.
~~~
$ minio init fs <path>
~~~

Minio initialize XL backend.
~~~
$ minio init xl <url1>...<url16>
~~~

For 'fs' backend it starts the server.
~~~
$ minio server
~~~

For 'xl' backend it waits for servers to join.
~~~
$ minio server
... [PROGRESS BAR] of servers connecting
~~~

Now on other servers execute 'join' and they connect.
~~~
....
minio join <url1> -- from <url2> && minio server
minio join <url1> -- from <url3> && minio server
...
...
minio join <url1> -- from <url16> && minio server
~~~

jwt.go

@@ -17,7 +17,6 @@
 package main
 
 import (
-	"bytes"
 	"strings"
 	"time"
 
@@ -28,8 +27,7 @@ import (
 
 // JWT - jwt auth backend
 type JWT struct {
-	accessKeyID     []byte
-	secretAccessKey []byte
+	credential
 }
 
 // Default - each token expires in 10hrs.
@@ -40,13 +38,11 @@ const (
 // initJWT - initialize.
 func initJWT() *JWT {
 	jwt := &JWT{}
-	// Load credentials.
-	config, err := loadConfigV2()
-	fatalIf(err.Trace("JWT"), "Unable to load configuration file.", nil)
 
 	// Save access, secret keys.
-	jwt.accessKeyID = []byte(config.Credentials.AccessKeyID)
-	jwt.secretAccessKey = []byte(config.Credentials.SecretAccessKey)
+	jwt.credential = serverConfig.GetCredential()
+
+	// Return.
 	return jwt
 }
 
@@ -57,7 +53,7 @@ func (jwt *JWT) GenerateToken(userName string) (string, *probe.Error) {
 	token.Claims["exp"] = time.Now().Add(time.Hour * tokenExpires).Unix()
 	token.Claims["iat"] = time.Now().Unix()
 	token.Claims["sub"] = userName
-	tokenString, e := token.SignedString(jwt.secretAccessKey)
+	tokenString, e := token.SignedString([]byte(jwt.SecretAccessKey))
 	if e != nil {
 		return "", probe.NewError(e)
 	}
@@ -68,9 +64,9 @@ func (jwt *JWT) GenerateToken(userName string) (string, *probe.Error) {
 func (jwt *JWT) Authenticate(userName, password string) bool {
 	userName = strings.TrimSpace(userName)
 	password = strings.TrimSpace(password)
-	if !bytes.Equal([]byte(userName), jwt.accessKeyID) {
+	if userName != jwt.AccessKeyID {
 		return false
 	}
-	hashedPassword, _ := bcrypt.GenerateFromPassword(jwt.secretAccessKey, bcrypt.DefaultCost)
+	hashedPassword, _ := bcrypt.GenerateFromPassword([]byte(jwt.SecretAccessKey), bcrypt.DefaultCost)
 	return bcrypt.CompareHashAndPassword(hashedPassword, []byte(password)) == nil
 }