event-manager

@kadst43 @eric79 This is just a start of converting our event listeners to use the event manager. It's pretty simple, you just need to implement the `eventManager` behavior on every node that will broadcast or listen for events. Listeners need to have a method to use as a callback and the event/callback pair added to the `eventMap`. This PR may not go in right away, but I wanted to get samples for you guys to look at.

Requires: https://github.com/virtual-world-framework/vwf/pull/400
You can write this as:

    eventMap:
      changedPOV: handlePOVChange