🦜 Implement `ElasticEvent` to allow magic treatment of `EventManager#callEvent`

[nuriofernandez]

Implement a way to handle events after his completion open to different implementations.

eventManager.callEvent(new NormalEventExample());

eventManager.callEvent(new ConsumibleEventExample()).onComplete(() -> {
    System.out.println("Event completed callback");
});

String name = eventManager.callEvent(new StringEventReturningExample());

[nuriofernandez]

Testing class:

import me.nurio.events.EventManager;
import me.nurio.events.ReflectedEventHandler;

public class ElasticEventTest {

    public static void main(String[] args) {
        EventManager eventManager = ReflectedEventHandler.createEventManager();

        eventManager.callEvent(new TestEvent()); // void

        AsyncResponse asyncResponse = eventManager.callEvent(new TestConsumableEvent());

        eventManager.callEvent(new TestConsumableEvent()).onComplete(() -> {}); // void

        String text = eventManager.callEvent(new StringReturnerEvent());
    }


    public static class TestEvent extends Event {}
    public static class TestConsumableEvent extends ConsumableEvent {}
    public static class ConsumableEvent extends ElasticEvent<AsyncResponse> {}
    public static class StringReturnerEvent extends ElasticEvent<String> {}

    interface AsyncResponse {
        void onComplete(AsyncFunction asyncFunction);
    }

    @FunctionalInterface
    interface AsyncFunction {
        void onComplete();
    }

}