Show formatted date in history

This PR shows the date (in history) in a translateable format. You can even change it to a relative format.
Added:
* [`moment.js`](http://momentjs.com/) (MIT licensed), a third-party library to format and use dates. It includes translations for many languages so that the relative date looks great either way.
* `requirejs-config.json` - sorry, but we need that file to get it to work. No other way :(
* A new setting whether to use relative date (default true)
* Translations for this setting
![image](https://f.cloud.github.com/assets/2641501/2492448/31201934-b22e-11e3-9d60-b96e7fae84d1.png)