Add localization

[Valefant]

We would like to have the possibility to localize the content we have on the site so far. There are several possibilities to choose from.

• Fill the text with javascript when the user visits the site
• Link to other html files in other languages
• Use a template engine and and localize the content according to the Accept-Language in the HTTP Header (in this case we could not use Github Pages anymore as we would need to host our own webserver)

There are plugins for jekyll which deal with localization. The only problem is that Github Pages doesn't support these plugins.