Update strings.xml
Update strings.xml

* Added 'German-Umlaute' äÄ,öÖ, üÜ and ß to translations so far
* Integrated recent changes from https://github.com/plinioseniore/soulissapp-plinio/commit/7b230a989fd71fae4b3daf431eb327fb3516192b
as highlighteed by Dario
*Proceeded with further translations
souliss/soulissapp