- inherit from Gaudi::Algorithm instead of GaudiAlgorithm to remove (amongst others) warnings that this algorithm is not (recognized as being) re-entrant
- prefer ServiceHandle over bare pointer, explicit property and call to service(...)
- use traverseTree instead of objectLeaves to make this work with evtStoreSvc (which does not implement objectLeaves because it cannot...)
required for (and motivated by) !3647