Co-authored-by: Andre Sailer <andre.philippe.sailer@cern.ch>

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This avoids a test failure when DD4hep is built with
DD4HEP_USE_GEANT4=OFF

CMake: add settings DD4HEP_BUILD_PACKAGES to chose which packages to build, DD4HEP_BUILD_EXAMPLES to build examples

it will be the responsible of the user to chose a working combination and order of packages
Use DD4hep::<Package> so that cmake will fail if required package was not enabled

   a flag wordL DetType
 - added test_DetType.cc

add currentEventNumber function to check which event one is at
Add small input files for the different event readers

Implement cellDimensions Functions for PolarGridRPhi and PolarGridRPhi2
Implement unit tests
Correct documentation string in CartesianGrid[XY]Z

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)