Convert the Linux / CUPS version of the QPageSetupDialog to use
QPageSize and QPageLayout internally.  As this is an almost complete
re-write of the internals the liberty has been taken of doing renames
and code moves that would normally be done in separate commits, but in
this case would have been mostly pointless done separately.

Change-Id: I6eaa7c1fbf0a04cb3425f1d322fcae89239e83b7
Reviewed-by: Lars Knoll <lars.knoll@digia.com>