Change number of labels to print based on category content

[jsubhi]

level: low
This is a special requirement for HAWK Hildesheim: They use a special code in Category 8075 to automatically determine the number of labels to print for this item.

(Backround: When books have a dust jacket (Schutzumschlag) both the jacket and the book get their own label - therefore two labels need to be printed. This information is added to category 8075 during cataloguing)

I will try to add this feature myself at a later date.