[timed] Run as user

- Voland service moved to session bus
- Spec file adds CAP_SYS_TIME required for settimeofday
- Event db file events.data and settings.data are written to
  QStandardPaths::writableLocation(QStandardPaths::DataLocation)
  in Qt5, in Qt4 they go to
  QDesktopServices::storageLocation(QDesktopServices::DataLocation)
[timed] Notify systemd that timed is up and running

When timed is passed the command line switch --systemd, then
it notifies systemd when it is ready.