Upgrade to SI 4.0

* Add new correlation endpoint options
* Add `messageStore` to the `PriorityChannelSpec`
* Add generic to `EnricherSpec#property`
* Remove `type` from `EnricherSpec.headerExpression`
* Add `initialDelay` for `PeriodicTriggerSpec`
* Fix `IntegrationFlowBuilder` bugs, when there is no relevant the end of the flow
* Add embedded MongoDb support for tests
* Add `priority` test with `MongoDbChannelMessageStore`
Replace `LiteralExpression` to `ValueExpression`
MQTT: Add README note: Moved to Spring Integration
DSL: Upgrade to SI 4.0. RELEASE
DSL: Clean up `README.md`
[artifactory-release] Release version 1.0.0.M1
[artifactory-release] Next development version
DSL: Add `MessageProducer` support
DSL: Add fluent `Transformers` factory
DSL: Add `IntegrationFlows.from(MGSupport)`

* Introduce `Amqp` components factory
* Add `AmqpInboundGatewaySpec` builder
DSL: add `gateway()` EIP-method

* Upgrade dependencies
* Polishing `Transformers`
DSL: Add `LambdaMessageProcessor`
DSL: Add `@Autowired @Lazy` test
SMPP: Fix typo in README

PR: https://github.com/spring-projects/spring-integration-extensions/pull/71
DSL: Tests for `@Autowired` handlers
DSL: Clean up some `IntegrationFlowBuilder` API
MQTT - Use INT/SPR 4.0.0

Conflicts:
	spring-integration-mqtt/build.gradle
MQTT - Update to Spring Integration 4.0.0.M1

Conflicts:
	spring-integration-mqtt/build.gradle
[artifactory-release] Release version mqtt 4.0.0.M1
[artifactory-release] Next development version