Add `--page-numbering` option for supplying page label ranges

[michaelmhoffman]

Currently, pdfcomments prints out page labels before each comment that are always the page index plus 1. It would be better if page labels defined within the document would be respected (#8). But even then, many documents will not have satisfactory page labels defined and users will want to manipulate them (#5). A flexible option should eventually allow supplying different ranges for changing what gets used as a label.

--page-numbering (-p for short) is something that makes some amount of sense whether a full range is provided, a series of ranges, or just a simple offset. Ranges can be:

• start
• start-
• start-end

Both start and end are inclusive—it is a fully closed interval. A series can be a series of ranges separated by ,.

Examples for a 6-page PDF:

• pdfcomments --page-numbering=2, pdfcomments --page-numbering=2-, or pdfcomments --page-numbering=2-7 would number the pages 2, 3, 4, 5, 6, 7.
• pdfcomments --page-numbering=2-5,99, pdfcomments --page-numbering=2-5,99- pdfcomments --page-numbering=2-5,99-100 would number the pages 2, 3, 4, 5, 99, 100.

If END is used and there are pages beyond that, the default numbering is used for those pages: page index+1 for now, but page label once #8 is implemented.