Added German translation

Hi @nikolov-tmw!

Great plugin! It's awesome that someone finally is developing an alternative to qTranslate.
Thank you for all your work. I want to help you and to begin with I translated the plugin in German. I am from Switzerland so there can be «errors» like the absence of ß (in Switzerland we don't use this letter, instead there will be «ss») and our quotation marks are « and » (instead of the „ and the “).

I've seen some errors at the original language-strings which I'll review as soon as I can.

Again, thanks for your work!