Prettify Multifields UI

Addresses #71

- Uses Dashicons for the icons ( http://melchoyce.github.io/dashicons/ )
- Example screenshots below:


![multifields_ui](https://f.cloud.github.com/assets/1083995/2222356/8d3eac1c-9a64-11e3-89fe-f72fc651c5fc.png)