Event - Create QueuedSubscriber

[MakoEnergy]

Currently there is an EventSubscriber class that doesn't really do anything in the Event system. It is intended to be the base class for some prefab subscribers to be provided for convenience.

One of the more important prefabs is a subscriber that will queue dispatched Events for delayed processing. That way it can be used across subsystems and be handled during that respective systems workunit. Expecting immediate processing always can and will lead to race conditions.

A possible candidate for inclusion in the Mezzanine:
https://github.com/cameron314/concurrentqueue