Add extra values to passport record

Hello, 
This is not necessarily the best method to implement this feature but I try to do something.
I am a newbie on NodeJS, Sails.

The generator is limited to the strict minimum. I wanted a flexible way to define what passport must saved. I  inspired by HWI/OAuth for Symfony. 

The principle is to define the mapping information in a section `paths`: 
* `localname` is the name of the value in the model/record
* `jsonname` is the key in `profile._json` 

For exemple :
```js 
github: {
     name: 'GitHub',
     protocol: 'oauth2',
     strategy: require('passport-github').Strategy,
     options: {
       clientID: 'your-client-id',
       clientSecret: 'your-client-secret'
     },
     paths: {
       localname: 'jsonname'
     }
   }
```

*If this pullrequest is not merge, I hope you like the idea and it will be integrated in the future*