INT-3423 Fix Expression-Based Splitter

JIRA: https://jira.spring.io/browse/INT-3423

Consider a message containing "one one" and a splitter
with expression "payload.split(' ')", only one message
is emitted.

The default Collection created by SpEL is a HashSet.

Change the ExpressionEvaluatingSplitter to expect a
List instead of a Collection.
Update to Spring AMQP 1.3.4, Groovy 2.3.1

Also change rabbit tests to use "localhost" explicitly;
newer brokers don't allow guest except on localhost.
[artifactory-release] Release version 4.0.2.RELEASE
[artifactory-release] Next development version
INT-3418: Prepare 4.1 VERSION

JIRA: https://jira.spring.io/browse/INT-3418

* Create 4.1 XSD
* Clean up Docs for 4.1
* Prepare WebSocket module
* Add Reactor dependency
* Remove Eclipse and SNV artifacts

Phase #1: prepare

Conflicts:
	gradle.properties
Phase #2: xsd-1.0 -> 4.1
Phase #2: xsd-2.0 -> 4.1
Phase #3: xsd-2.1 -> 4.1
Phase #4: xsd-2.2 -> 4.1
INT-3418: Phase #4: xsd-2.2 -> 4.1
INT-3418: Phase #6: xsd-4.0 -> 4.1
INT-3418: Final Phase: Cleanup