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

 Added one more if statement: If the track went into new Volume, then extracted the hit in previous Volume, and start a new hit in this current Volume. And in this current process, also allow the same following treatments for the new hit.

TrackerWeightedAction: Fix defaults which caused an empty hit to be stored which broke the MCHistory

 - removed random lines drawn in teveDisplay
 - dont't print DetectorData by default in dumpdetector

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