-D DD4HEP_USE_BOOST -D BOOST_ROOT=_path_to_boost_
 - client packages will automatically also use boost 
   ( add_definition( DD4HEP_USE_BOOST )) 
   

   (overwrite w/ -D CMAKE_BUILD_TYPE=Debug, Release,...)

    - 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