Fix wrong Xi2 for 5hits track
StiDetector: Removed pointer to StiElossCalculator from the class. The objects of StiElossCalculator are referenced now in StiMaterial
StiMaterial: Associated StiElossCalculator with StiMaterial by adding a new member pointer to the class
Removed any explicit reference to StiElossCalculator in all StiDetectorBuilder's. StiElossCalculator is now a member of StiMaterial where it is created and managed
Removed any explicit reference to StiElossCalculator in all StiDetectorGroup's. StiElossCalculator is now a member of StiMaterial where it is created and managed
Access StiElossCalculator from StiMaterial instead of StiDetector. StiElossCalculator is now a member of StiMaterial where it is created and managed
StiKalmanTrackNode: Corrected Eloss calculation
StiTrackNodeHelper: Corrected Eloss calculation