man pages: add translation into German
Update AUTHORS and ChangeLog
Windows installer: include German man page translation
Translations: fix header comments with focus on copyright

Fixed issues:

- no copyright at all
- incomplete copyright (missing persons)
- incomplete copyright (years incomplete)
- copyright allegedly assigned to the Free Software Foundation due to
  the original file being auto-generated by msg*
Translations (man pages): update list of translatables
Translations (man pages): update German translation
mmg: prevent saved window widths growing by 1 pixel
Update italian translation