Rework translation credits

[tobbi]

Currently, it's just a blob of text.

I'd suggest splitting those credits by language. We could have something like:

-- German
Name 1, name 2, name 3..n

Is much more compact and easier to read for people who are interested.

[maxteufel]

I think credits in general should be reworked. They're currently a bit out of date anyway, and aren't nicely structured.