Add @PropertySources and ignoreResourceNotFound

Support repeatable @PropertySource annotations in Java 8 and add
@PropertySources container annotation for Java 6/7. Also add an
ignoreResourceNotFound attribute to @PropertySource allowing missing
property resources to be silently ignored.

This commit also introduces some generally useful methods to
AnnotationUtils for working with @Repeatable annotations.

Issue: SPR-8371
Fix broken test in MvcNamespaceTests

The testDefaultConfig() method in MvcNamespaceTests creates a new Date()
in its test fixture but then performs an assertion against a hard coded
data string of "2013-10-21". This test therefore only passed yesterday,
on October 21, 2013.

This commit addresses this by changing the hard coded date string to one
based on the current date.

Issue: SPR-10665, SPR-8826
Switch to reactor snapshots and make use of API change
Add ListenableFuture to TcpOperations connect methods
 Make changes for timing related test failures
Add STOMP broker relay unit tests
Refactor HandlerMethod support in spring-messaging

Introduce base class AbstractMethodMessageHandler for
HandlerMethod-based message handling.

Add MessageCondition interface for mapping conditions to messages
with support for combining type- and method-level annotation
conditions, the ability to match conditions to messages, and also
comparing matches to select the best match.

Issue: SPR-11024
Upgraded to ASM 4.2
Only apply Groovy plugin to modules where it is actually needed