build all examples in one go
    - made necessary changes in package cmake files
      for this to work
    - updated documentation in Readme

   -> already in $DD4HEP_LIBRARIES

     Property& operator=(const std::string& val);
   as this is in conflict with explicit instantiation (using string) of:
     template <typename TYPE> Property& operator=(const TYPE& val);
  
   -> Need checking with other compilers !!