Feature request: Page concatenation during conversion

[jsbien]

Transkribus (https://readcoop.eu/transkribus/?sc=Transkribus), which just reached 100 000 users, export PAGE and ALTO as a single file for every page and the actual page numbers are not stored in the files. In my workflow ALTO -> hOCR-> dsed I have to edit the page numbers in *.dsed files before using them as a valid djvused input (to use the transcription as the hidden text layer in a DjVu document). It would be nice to solve the problem in a general and elegant way.