Refactor static asset data model and style dashboard

This refactors the data model behind the static asset admin dashboard, introducing ```AssetChart``` and ```AssetData``` classes.

Also adds some Bootstrap loving to the view and re-style the charts.

#### Screenshot
![google chrome](https://f.cloud.github.com/assets/80089/1844504/03e55cf6-7532-11e3-9745-52f98fb225d3.png)

/cc @gklopper can you please give my Scala foo a once over.