Integrate events into entity_manager about entityplus HOT 2 CLOSED

There will need to be a partial specialization to specify the component_list and tag_list to event_manager so that it can be broadcast to by entity_manager. Although this can be messy, it is possible. The only problem is that this feature is very weak unless you can actually store entities in some outside containers.

An example usage is a quadtree that tracks any entity that moves, but also adds and removes entities if they have a position component added/removed. To accomplish this functionality you would need to store the position and also the entity it is associated with, and to do that you need storeable entities. Issue #13 was created to address this.

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There had to be some compromises due to compiler deficiencies but I think the end result is strong. Now the event manager needs the first two types to be component_list and tag_list, just like the entity manager, but an entity manager will work with any event manager as long as their components/tags are the same.

The only step left is to document the changes and the new events and when they are broadcast.

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