Add support for advanced page ranges

Currently specified page ranges are de-duplicated, sorted into ascending order and doesn't allow reverse ordering. This means that the following happens:

input | output
2-4,1-3 | 1,2,3,4
5-3 | invalid

Some other applications seem to allow reverse ordering and duplication, but they instead print the pages given in the order given. Which means that the following happens:

input | output
2-4,1-3 | 2,3,4,1,2,3
5-3 | 5,4,3
5-3,4-6 | 5,4,3,4,5,6

It also appears that they don't set the page-rages attribute on the print job in CUPS, so I suspect that they are rendering an intermediate PDF which has this ordering before handing to CUPS.