add i18n setup

Closes #11 (closed)

Info: Basic functionality included. There are two ways of this to be used later on… as an instant language switcher and having the language added automatically by i18n to the URL as parameter.

I build an example on the index page for both cases.

The instant language switcher is faster and easy to handle but all languages need to be loaded in advance and cannot be loaded lazily. It's not recommended for huge language files but I doubt that we will have that much text on the Portal and I would like to give it a try because it's REALLY fast.

Opinions @jan.schweikert @steinm01 ?