Adds Publisher abstraction that implements pub/sub model to deliver events from publisher to subscriber.
Replaces CompositeEthereumListener / EthereumListenerAdaptor / EthereumListener using with new event publishing mechanism.
Keeps backward compatibility with old event handling model.
Coverage decreased (-0.07%) to 56.169% when pulling 698b59a267f560a1853800239410cb67bb64c3e0 on feature/1138-event-listener-improve into 5c808c1ddfd743e668386d94ec68b6ba3f7713dd on develop.
This PR covers issue #1138.
Adds Publisher abstraction that implements pub/sub model to deliver events from publisher to subscriber. Replaces CompositeEthereumListener / EthereumListenerAdaptor / EthereumListener using with new event publishing mechanism. Keeps backward compatibility with old event handling model.