second part of the jpf-statechart motivated event interface overhaul, providing dynamic (context specific) expansion of EventTrees from within EventChoiceGenerators. This adds a EventContext mechanism that can replace events on-the-fly during advance() (e.g. expand wildcard patterns) this also included the refined 'vm.extend.transitions' property, which is now a list of TypeSpecs (glob notation plus bounds) for CG types that should be subject to transition extension. We also support CheckExtendTransition attrs for CGs, which can be used to dynamically mark CGs. Note that each matching CG is still tested for non-rescheduling single choices small Type/FeatureSpec extension to make it applicable to java.lang.Class instances. There is no reason why we can't make use of this for native types