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