added inverse matching in StringSetMatcher. Since this is not easy to do in regexes, it's at the next hight level in StringSetMatcher added a optional CG accessor interface (geChoice(i), getAllChoices(), getProcessedChoices() getUnprocessedChoices()) that can be used from listeners and peers to enumerate/analyse choice sets. Note that not all CGs have to support this as there is no requirement that CGs actually use pre-computed choice sets. The low level accessor is getChoice(i), ChoiceGeneratorBase provides generic (not very efficient) set accessor implementations. Note that ChoiceGeneratorBase.getChoice() has to be overridden in subclasses in order to support choice enumeration, the default impl is just there so that we don't break subclass compilation