- moved the HUD state reset from a trigger action into the scenario's start() function
- got the global triggers hooked up, loading, and resetting when scenarios change.  This did away with the
  functionality of the late load triggers (although some of the framework is still there - to be cleaned up
  once we solve that problem "for real.")
- we no longer fire an event when the blackboard is written, as this could cause other triggers to fire
  immediately (and was also resulting in an infinite recursive call when the same trigger keeps triggering
  itself)
- Changed a lot of places that were using the blackboard to not repeat so that they use the doOnce clause
  instead
- made the triggerManager a scene getter, so that the global scenario triggers wouldn't have to keep a local
  variable of the scene.