Establish system for i18n

[kaiec]

We need full translations, not only of the API but also of all text printed to stdout so that we can give meaningful feedback where possible.

The addition and maintenance of further languages has to be as easy as possible. For the API translations, it is important that they work in editors with auto completion, so no dynamic generation of the functions, but a script that generates the api from translation files could be a good idea.

There are systems like gettext (included in Python) or modules like python-i18n, they could be worth another look, but currently I think a simple system using JSON files would be enough.

[kaiec]

Work in progress:

44ae8d0 Moving some files - kaiec
96edb73 Rewritten translation system - kaiec