German translation

* Please review the annotations related to [localization best-practices](http://developer.android.com/guide/topics/resources/localization.html) and fix them if possible.
* I can't test the "look-and-feel" of the application after the sign-up-process, since I am unable to connect to my server (issue #19, #22).
* I would appreciate some response of someone testing the UI usability with a Flock Sync account.
* It would be nice if the UI designers respect the long words in some non-English languages...
* Please provide some information about the BitHub integration, announced on [this](https://whispersystems.org/blog/flock/) page.