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
~~~

config-old.go

@@ -0,0 +1,81 @@
+package main
+
+import (
+	"os"
+	"path/filepath"
+
+	"github.com/minio/minio/pkg/probe"
+	"github.com/minio/minio/pkg/quick"
+)
+
+/////////////////// Config V1 ///////////////////
+type configV1 struct {
+	Version         string `json:"version"`
+	AccessKeyID     string `json:"accessKeyId"`
+	SecretAccessKey string `json:"secretAccessKey"`
+}
+
+// loadConfigV1 load config
+func loadConfigV1() (*configV1, *probe.Error) {
+	configPath, err := getConfigPath()
+	if err != nil {
+		return nil, err.Trace()
+	}
+	configFile := filepath.Join(configPath, "fsUsers.json")
+	if _, err := os.Stat(configFile); err != nil {
+		return nil, probe.NewError(err)
+	}
+	a := &configV1{}
+	a.Version = "1"
+	qc, err := quick.New(a)
+	if err != nil {
+		return nil, err.Trace()
+	}
+	if err := qc.Load(configFile); err != nil {
+		return nil, err.Trace()
+	}
+	return qc.Data().(*configV1), nil
+}
+
+/////////////////// Config V2 ///////////////////
+type configV2 struct {
+	Version     string `json:"version"`
+	Credentials struct {
+		AccessKeyID     string `json:"accessKeyId"`
+		SecretAccessKey string `json:"secretAccessKey"`
+		Region          string `json:"region"`
+	} `json:"credentials"`
+	MongoLogger struct {
+		Addr       string `json:"addr"`
+		DB         string `json:"db"`
+		Collection string `json:"collection"`
+	} `json:"mongoLogger"`
+	SyslogLogger struct {
+		Network string `json:"network"`
+		Addr    string `json:"addr"`
+	} `json:"syslogLogger"`
+	FileLogger struct {
+		Filename string `json:"filename"`
+	} `json:"fileLogger"`
+}
+
+// loadConfigV2 load config version '2'.
+func loadConfigV2() (*configV2, *probe.Error) {
+	configFile, err := getConfigFile()
+	if err != nil {
+		return nil, err.Trace()
+	}
+	if _, err := os.Stat(configFile); err != nil {
+		return nil, probe.NewError(err)
+	}
+	a := &configV2{}
+	a.Version = "2"
+	qc, err := quick.New(a)
+	if err != nil {
+		return nil, err.Trace()
+	}
+	if err := qc.Load(configFile); err != nil {
+		return nil, err.Trace()
+	}
+	return qc.Data().(*configV2), nil
+}