Needed to access cell dimensions in a segmentation agnostic way
Implemented unit tests for cellDimensions
Implemented default function throwing exception
Implemented cellDimensions for CartesianGridXY, XZ, YZ, XZY
Added c++11 definition to DD4hep.cmake (implemented functions with and without c++11)

Split libraries into DDCore and DDComponents.
One has to explicitely specify the required components in find_package.
See doc/release.notes for more details

Call notapple function for macs at the moment. Forgot to change this function during refactoring

Split into apple and notapple functions, users just use dd4hep_generate_rootmap
removed commented code in generate_rootmap_apple

Add two cmake functions for creating dd4hep plugins (creating library and rootmaps and installing package env file)

   MacOS 
     -> requires all dynamic libraries to be on the search path ...

Make location of MakeRootMap.cmake to DD4hep_ROOT if it exists. In that case DD4hep is an external library. Now examples can be compiled against it.

   - use version suggested by A.Sailer for all but macos (APPLE)
   - added extra function dd4hep_generate_rootmap_apple()
     this version sources the thisXXX.sh scripts
     before running genmap - but does not seem to work for Linux
     -> needs to be resolved ...

    - ./bin/thisdd4hep.sh now initializes also ROOT
      and optionally geant4
    - cmake/thisdd4hep_package.sh.in is used in 
      examples to create thisILDExDet.sh and thisILDExSimu.sh
  
  - the thisdd4hep.sh script is now also used in the build process
    for generating the rootmap files

   w/ CMAKE_SHARED_LIBRARY_SUFFIX