Add song rating display support ★★★★★

Adds 2 more display options
- Title, Artist, Album, Rating
- Title, Artist, Album, Rating (Stacked)

The rating will be display as stars, with half star as well.

![screenshot 2014-09-03 10 29 07](https://cloud.githubusercontent.com/assets/248741/4129156/8b644254-331a-11e4-9780-a0b07d6bf23b.png)