Port K4AboutData, KCmdLineArgs and KUniqueApplication

Eliminates the runtime messages:

  kmix/kf5.kcoreaddons.kaboutdata KAboutData::setApplicationData: Could not initialize
  the equivalent properties of Q*Application: no instance (yet) existing.
  kmix/kf5.kcoreaddons.kaboutdata {anonymous}::warnIfOutOfSync:
  QCoreApplication::applicationVersion "" is out-of-sync with
  KAboutData::applicationData().version "4.6"
  kmix/kf5.kcoreaddons.kaboutdata {anonymous}::warnIfOutOfSync:
  QGuiApplication::applicationDisplayName "kmix" is out-of-sync with
  KAboutData::applicationData().displayName "KMix"
  kmix/kf5.kcoreaddons.kaboutdata {anonymous}::warnIfOutOfSync:
  QGuiApplication::desktopFileName "" is out-of-sync with
  KAboutData::applicationData().desktopFileName "org.kde.kmix"