New features/fixes:
Corrections DNG import function
Add chapter numbers to the displayed document for the print
Display the file name, document ID and the last change of the document on the cover sheet
Possibility to define / change the properties of attachments (MIME-Type)
External links: Description is a mandatory field
Bugfix handling of incorrect / incomplete links
Bugfix treatment of Multiple Spec ObjectType
Bugfix treatment of URL-encoded path details