20130201 easy server registration

tengine_resourceコマンドを実装しました。手動でTengine::Resource::PhysicalServerとTengine::Resource::Credentialの登録、削除と確認ができます。

```
% bin/tengine_resource server
Tasks:
  tengine_resource server add [name]      # add server
  tengine_resource server help [COMMAND]  # Describe subcommands or one specific subcommand
  tengine_resource server list            # list servers
  tengine_resource server remove          # remove server manually by using [name]


% bin/tengine_resource credential
Tasks:
  tengine_resource credential add [name]      # add credential
  tengine_resource credential help [COMMAND]  # Describe subcommands or one specific subcommand
  tengine_resource credential list            # list credentials
  tengine_resource credential remove          # remove credential manually by using [name]
```

それぞれのコマンドについての使い方は以下のように調べることができます。
```
% bin/tengine_resource credential help add
Usage:
  tengine_resource add [name]

Options:
  -f, [--config=CONFIG]                      # config to connect MongoDB as same as tengine_resource_watcher's config
  -u, [--username=USERNAME]                  # username to login
  -p, [--password=PASSWORD]                  # password
  -k, [--private-key-file=PRIVATE_KEY_FILE]  # private key filepath. ex. ~/.ssh/id_rsa
  -P, [--passphrase=PASSPHRASE]              # passphrase for private key
```

詳しくは以下のクラスをご覧ください。
https://github.com/tengine/tengine/blob/20130201_easy_server_registration/tengine_resource/lib/tengine/resource/cli/server.rb
https://github.com/tengine/tengine/blob/20130201_easy_server_registration/tengine_resource/lib/tengine/resource/cli/credential.rb