Update stringtable.xml

Added  german localisation
Corrected some spelling mistakes

Not sure at: 
-line 55 / Flummi ?

I also suggest to change "Wähle einen Zünder" to "Zünder wählen" (l. 235)
Merge pull request #967 from licht-im-Norden87/patch-4

Update stringtable.xml