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

Allow for sensitive actions with multiple readout segmentation in the Geant4Sensitive action sequence

Keep sensitive detector type constant. Add property to Geant4Kernel if special/user defined G4VSensitiveDetector instances should be created

Support for multi-threaded Geant4 applications using DDG4Details are described in the release notes.

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.

Hopefully I got the assemblies right now. Assembly test added in examples/ClientTests. Please see also doc/release.notes