net-print/hplip: Rework USE logic, fix python deps

net-print/hplip: Rework USE logic, fix python deps

Gentoo-bug: 594532, 586256

- Added missing PyQt5[widgets] USE dependency.
- Fix pygobject slotdep
- Build system gives no indication why not both qt4 and qt5 could be
  installed but retain existing behaviour anyway by turning qt4 into !qt5.
- USE=!minimal now means some kind of GUI is installed, be it Qt4 or Qt5.
  It means sys-apps/dbus becomes conditional only to USE=minimal as well.
- USE=fax depends on python2
- Dropped eutils.eclass
- eapply -> PATCHES array, D -> ED
- Cleaned up some ancient version deps

Package-Manager: portage-2.3.0

Signed-off-by: Daniel Pielmeier <billie@gentoo.org>