This adds another 'FilePrinter::printFile' method that
accepts an additional parameter to specify whether or not to
do scaling and passes the 'fit-to-page' to CUPS dependent
on what is specified.
If FilePrinter is used, The PDF generator now passes this
option depending on the scaling mode that was selected in the
custom print options widget, which is therefore now enabled
for non-rasterized printing as well.