German comments

[thorade]

There are some comments in German that should be translated or removed or moved into a proper documentation. Search for:

• [x] derzeit
• [x] alte
• [x] Waende
• [x] Netto
• [x] brutto
• [x] davon
• [x] Kennlinien
• [x] ausgehend
• [x] Abhaengigkeit
• [x] Gueltigkeitsbereich
• [x] Luft
• [x] Enthalpie
• [x] Druck
• [x] Dampf
• [x] Saettigung
• [x] und
• [x] ist
• [x] ä
• [x] ü
• [x] ö

To be continued...

[jmoeckel]

Extended the list by some typical words and language-specific letters.