Overload function 'Geant4HitData::extractContribution' with 'bool ApplyBirksLaw' for extracting the MC contribution for a given hit from the step information with BirksLaw effect option. 

Fix hundreds of std=c++11 compiler warningsAllow to change compiler settings in cmake/DD4hep.cmake valid for all packages.Watch out for CMAKE_CXX_FLAGS in cmake/DD4hep.cmake.Move to use Boost spirit::phoenix version 3. ---- Prepare for ROOT 6

Add component to allow the setup of the magnetic field tracking in Geant4 from python. See DDG4/examples/CLICSidSimu.py for the usage.

No code changes. Common code formatting removing tabs, replacing with spaces (tab-size=-2) + emacs reformatting.

First implementation of dipole field, HepMC reader for DDG4 and fix to import constants into DDG4 python