Add german translation (#536)

* add german translation

* add german to language list

* donttranslate language names. always use the native name.

* add compiled german translation file

* german translation handling

* add german to getSuffixFromLanguage

* update german string and translation

* update all language files with new strings

* typo

* compile

* more typos and fixes for german

app/app.pro

@@ -321,6 +321,7 @@ RESOURCES += \
 
 TRANSLATIONS += \
     languages/qml_zh_cn.ts \
+    languages/qml_de.ts \
     languages/qml_fr.ts
 
 # Additional import path used to resolve QML modules in Qt Creator's code model