DE accumulated fixes

Including latest regression-fixes ( !961 (merged) !959 (merged) , yes I separated the DE part to avoid merge conflicts )

Spell-corrected some words using a dictionary (mostly ss->ß), just like I did for French.

Not so minor fixes:

• E02 Translated the potion labels that were added later.
• E06P09 changed the cat referenco of Carrot from 'Katze'(Chatte) to 'Kater'(Chat)
• E34P09 wieder wieder (removed repeated word that occurred during the first translation improve process)
• E36 Credits fix in .svg (had unchanged EN contributions)
• E38 Added changes from branch german-update explained in #240 (comment 1986419) suggested by @kate (& added to credits)

• translated some references in de.po (Ratte, Wache, Feind, Phönix) 'extracted' from transcript or episodes
  DE E14P06 E27P02 improvements from @bmwiedemann !963 (merged) !964 (merged) (needs review - moved to new branch)
• DE EP36 transcript technical fix, part of !965 (merged)

Minor fixes:

• EP01-11: Removing extra spaces before ? ! : (and sometimes ...)
• EP01-06: Add full stops at the end of sentences.
• Some minor fixes in grammar (capitalisation)

I couldn't resist tweaking a few speech bubbles along the way.

If anyone wants to review the changes, I recommend checking the .md files.