[c#/de] german translation of c# tutorial

This adds a german translation of the C# tutorial.

As always, this can only benefit from a proof-read by a fellow native speaker or anyone else knowing what a Donaudampfschiffahrtselektrizitätenhauptbetriebswerkbauunterbeamtengesellschaft might be.

As this is a tutorial of rather epic length, I'd be very happy with partial input as well (i.e. you don't have to fix it *all*). I'm sure there's a lot of room for discussion, improvement and missing commas in there.

Thanks.