Localization

I've implemented the localization patterns we was talking about. There is still some space for improvements (I've left some TODOs in localization files for example) but that's the main framework. I've done my best to make the API clear and concise.

I think we should spin off some additional tasks (such as documenting the localization API in a distinct document and updating the localization files).
It means "at mr". I'll fix that.