Step/track actions updated

Optimized Geant4 StackingAction and SteppingAction classes - use G4Regions to identify detectors and not G4LogicalVolumes. This providing some CPU performance improvement and make code more clear.

SImTrack for decay and gamma conversion is saved by default independently of position in space (before this was only inside tracker). This increasing number of SimTracks for about 15%.

Flag to enable muon-nuclear interaction is propagated to all CMS Physics Lists, by default the flag is "false".

Neutron killer disabled by default, because CMSSW has its own filters of Geant4 tracks with more tight constrains.