Update de_DE.lang

There is actually only 1 word for corner, nook and notch, so it is not 100% verbatim. I had to improvise a little, but it should work.

P.S.: It was VERY hard to translate this stuff, since e.g. an actual notch is the opposite of what it is here (http://en.wiktionary.org/wiki/notch#Noun)...