DDCore and other packages now depend on DDSegmentation
Segmentation from DDCore now holds a DDSegmentation object that is created during XML parsing
Readout interface extended to act like a full IDDecoder combining information from the volume manage and the DDSegmentation object
TODO: Segmentation could be removed completely, if Readout simply holds a DDSegmentation object
TODO: Missing DDSegmentation classes for cylinders

    - DDExamples no longer built with DD4hep
      => will become standalone packages
    - moved UtilityApps from DDExamples to root level
      apps are built by default
    - create DD4hepConfig.cmake