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
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