The super constructor of implementors of TriggerActiveChangedListener.
TriggerActiveChangedListeners wish to be notified whenever a specific trigger changes from active to inactive or inactive to active. A trigger is active if it would cause a state change - that is, with the supplied context all it's validators would validate, and it would match a transition.
Active Changed(bCan Change, oContext, sEvent)
true if the trigger has become active, false if it has become inactive.
the data context.
is the trigger that has changed its active state.