Assume that the CUPS printer is able to handle collating by itself,
don't send multiple print jobs (except if user clicks on "Create single
print jobs for collated output" of course...).

To enable collating with PDF based printers, add the "collate" option;
legacy PS based printers still get the weird stuff read from the PPD
(not sure what the risks of changing that are).

Change-Id: Ia12dc69f9083bba94f2ed633ecbd153aac7e40ab