Refactored ChainDictFromName
This MR is changing the structure of the piece of code that translates ChainProp into the ChainDict. There was absolutely no reason for it to be a class. It was dangerous as the instantiated decoder could keep state and we could have ordering effects. In fact, while working on an issue reported by @khoo in specifying the jet thresholds I run in exactly that issue in the NewJO test. Was hell to debug! After this change, it will be simply impossible to fall into such a trap again. Tagging @bernius @jmontejo for menu side.