Add the background selection

#9 

In the book permits the player and his GM to customise the equipments, feature, language, skills etc.

The bonds, flaw, ideals and traits suggestions I think we can add later on the personality screen.

For now, we'll assume the background provide fixed options.

- [x] Display the backgrounds.
- [x] Show the backgrounds details.

![backgrounds-page](https://cloud.githubusercontent.com/assets/867308/5160121/cb169b70-7368-11e4-8904-9d56b96c554e.png)