Update German translation, mostly wrt orthography

Update German translation, mostly wrt orthography

Provide an update of the German translation.
* A lot of compound words were previously written with spaces, while
  German orthography is relatively clear in that the components
  should not be separated.
* When referring to the actual process of (de)compression rather than the
  concept, replace “(De-)Kompression” with “(De-)Komprimierung”.
  Previously, both forms were used in this context and are now used in a
  manner consistent with “Komprimierung” being more likely to refer to
  a process.
* Consistently translate “standard input”/“output”
* Use “Zeichen” instead of false friend “Charakter” for “character”
* Insert commas around relative clauses (as required in German)
* Some other minor corrections
* Capitalize “ß” as “ẞ”
* Consistently start option descriptions in --help with capital letters

Acked-By: Andre Noll <maan@tuebingen.mpg.de>
* Update after msgmerge