Added extra priorities to support Sponge

Sponge has 4 extra priority levels.  This expands the EventPriority enum so that the extra priorities are supported.

It also adds a .getBusID() method to the EventBus class.  This means that the Sponge event system can directly submit events to the ListenerLists associated with Forge events.
No, what are you wanting to do specifically. There should be nothing wrong with passing listeners in via the normal register function.