The DefaultEventBus is making poor choices in where to publish events.

• The immediate publish method publishes to the EDT. Thus if the result of this publish tries to do something on the EDT it will deadlock.
• The publishLater method uses ThreadService.run, which runs on an arbitrary thread. Thus subsequent publishLater calls are not guaranteed to execute in a consistent order.

To resolve this issue, we should have a dedicated SciJava event-processing thread which runs all EventBus publications.