Fix issue with sub-protocol negotiation and SockJS

Before this change the SockJsWebSocketHandler precluded determination
of the sub-protocols by wrapping the actual target handler.

After this change SockJsWebSocketHandler implements SubProtocolCapable
and returns the list of sub-protocols from the wrapped handler.
Add section on path pattern comparison

Issue: SPR-10576
Update RestTemplate Javadoc

Issue: SPR-10497
Update UriTemplate Javadoc

Issue: SPR-10497
Fix documentation issue for user destinations

Issue: SPR-11992
Enrich documentation with details on how to filter messages

Issue: SPR-11952
Polish