branch/event-manager

@kadst43 @eric79 Here's the event manager driver and behavior. It's really simple and it works. Let me know what you think.
I did the setting property thing at first, but I don't like it. I think it's counter-intuitive to set something to itself in order to trigger some hidden background process. I would advise against doing that. You could imagine new developers to VWF seeing an assignment like that and either being confused or assuming that it is a mistake. I think I'll just remove this functionality for now. I'm not using it and I don't know that it's necessary.