PartProps:- Add new symbols for "nodes"
- C++ types : PosID & NegID
- python instances: PosId & NegId
- symbols: ID+ & ID- New symbols to probe positive or negative PID. They are useful is useful in conjunction with other metasymbols, e.g. "Charm & ID+" will define particle with single charm quark and "Charm & ID-" matched particle with single anti-charm quark
Clearly these are not very well defined symbols (for eg. charmonia), but stil they are very useful