D7962: Implement several new print scaling options

[Nathaniel Graham]

ngraham added a reviewer: VDG.

REPOSITORY
  R223 Okular

REVISION DETAIL
  https://phabricator.kde.org/D7962

To: sander, #okular, aacid, #vdg
Cc: okular-devel, cfeck, rkflx, michaelweghorn, ngraham, aacid