Add track momentum to the MonteCarloContribution of Geant4Hit structures. See issue https://github.com/AIDASoft/DD4hep/issues/1037

Implement fast simulation shower modelling. Simplify GFlash to use the same sensitive actions as fast simulation

Add test to dump hits from MultiSegment-MultiCollections example. Investigate issue: https://github.com/AIDASoft/DD4hep/issues/141 for details

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

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

Improved version of MC particle handler, fix calorimeter hit aggregation with multiple contributions