Use correct header for version in CONNECTED frame

Previously, the negotiated version was included in the CONNECTED frame
using the accept-version header. This is incorrect. The version
header should be used.
Add StompProtocolHandler tests
Added 'zone' attribute to @Scheduled

Issue: SPR-10456
Added conversion support for Java 8's ZoneId class and the 'of' method convention

Issue: SPR-1528
Polishing
Add option to remove path ext in ServletUriCompBuilder

Issue: SPR-10272
Add basic javadoc to spring-messaging annotations
Add support for Ping and Pong WebSocket messages

Issue: SPR-10876
Release version 4.0.0.M3
Increment version to 4.0.0.BUILD-SNAPSHOT
Fixed getCachedExecutor race condition in MethodReference

Issue: SPR-10884
Remove incorrect package import

Issue: SPR-10880
Polish WebSocket/STOMP Java config

Ensure configuration provided for WebSocketHandler's (eg interceptors,
or HandshakeHandler) are passed on to the SockJsService if congiured.

Better separate Servlet-specific parts of the configuration to make it
more obvious where non-Servlet alternatives could fit in.

Add more tests.

Improve WebSocket integration tests.
Add Tomcat WebSocket integration tests
Polish WebSocket integration tests