EventManager: added syndrome event.
EventManager: fixed a few things.
EventManager: got rid of print statement.
EventManager: added invasion event.
EventManager: Fixed a problem with deregistering event frequencies.
EventManager: made the frequency part of EventHandler.
EventManager: use WORLD_LOADED instead of MAP_LOADED.
Auto syndrome: got rid of allow multiple syndromes option that didn't make any sense, and made sure that if allowing multiple targets it doesn't attach the syndrome to the worker twice.
Merge branch 'eventManager' into autoSyndrome