Updates to AtlasSematics: Defaults + PublicToolHandles
Few more updates to AtlasSemantics.py (preparation for GaudiConfig2):
- Implement default( .. ) method, mostly to work around Gaudi-issue gaudi/Gaudi#114 (closed)
- Implement Semantics for ServiceHandles and PublicToolHandles, effectively turning them into strings as they are just pointers to something that is configured elsewhere