INT-4390: Fix tangles

JIRA: https://jira.spring.io/browse/INT-4390

Phase I: flow context/registration cycle

- extract interfaces
- rename implementations to `Standard...`

Phase II - dsl<->dsl.channel tangles

Move the channel specs to dsl.

Fix missing refactorings

(Not related to DSL) - rename core `event` package to `events`

- avoid collision with event module package
- fix tangle caused by `MessageGroupExpiredEvent`.

Phase III - dsl<->config.dsl

- move classes from config.dsl to dsl

(Not related to DSL) - fix many tangles caused by graph being a sub-package of support.management
 - make `graph` a top-level package

(Not related to DSL) - move `IntegrationManagementConfigurer` from
`management` to `config` - tangle between core and management
* Polishing Copyrights, diamonds, some JavaDocs and What's New

spring-integration-stream/src/main/java/org/springframework/integration/stream/StreamClosedEvent.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2016 the original author or authors.
+ * Copyright 2016-2018 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -16,12 +16,13 @@
 
 package org.springframework.integration.stream;
 
-import org.springframework.integration.event.IntegrationEvent;
+import org.springframework.integration.events.IntegrationEvent;
 
 /**
  * Application event published when EOF is detected on a stream.
  *
  * @author Gary Russell
+ *
  * @since 5.0
  *
  */