Drop unused concept of shared child particle barcodes

A long time ago, there was the idea that all child particles produced in a decay could be assigned the same barcode. This schema was never used and now we are migrating away from barcodes generally it seems like a good time to clean this unused code up.

• TruthSvc: Drop setSharedChildParticleBarcode method
• IBarcodeSvc + implementations: Drop sharedChildBarcode method
• ITruthIncident + implementations: Drop setAllChildrenBarcodes method
• ISFParticle: Drop unused setBarcodeAndUpdateHepMcParticleLink method (this was only called by ISFTruthIncident::setAllChildrenBarcodes)

Simulation/ISF/ISF_Core/ISF_Event/ISF_Event/ISFParticle.h

@@ -157,8 +157,6 @@ namespace ISF {
     int barcode() const; // FIXME barcode-based
     /** set a new barcode */
     void setBarcode(int bc); // FIXME barcode-based
-    /** set a new barcode and update the HepMcParticleLink  */
-    void setBarcodeAndUpdateHepMcParticleLink(int bc); // FIXME barcode-based TODO Update this method to use the unique ID rather than the barcode.
 
     /** unique ID */
     int id() const;