Enhance MessageHeaderAccessor support

Refine semantics of ID and TIMESTAMP headers provided to protected
MessageHeaders constructor.

Refactor internal implementation of MessageHeaderAccessor.

Support mutating headers from a single thread while a message is being
built (e.g. StompDecoder creating message + then adding session id).

Improve immutablity in NativeMessageHeaderAccessor and in
StompHeaderAccessor.

Optimize object creation for initializing messages and subsequent
accessing their headers.

Introduce MessageHeaderAccessorFactory support to enable applying a
common strategies for ID and TIMESTAMP generation to every message.

Add MessageBuilder shortcut factory method for creating messages from
payload and a full-prepared MessageHeaders instance. Also add
equivalent constructors to GenericMessage and ErrorMessage.

Issue: SPR-11468
Make use of enhanced MessageHeaderAccessor support

Mutate rather than re-create headers when decoding STOMP messages
before a message is sent on a message channel.

Use MessageBuilder.createMessage to ensure the fully prepared
MessageHeaders is used directly MessageHeaderAccessor instance.

Issue: SPR-11468
Support mutable headers in MessagingTemplate

AbstractMessageConverter and messaging template implementations now
detect and use mutable headers if passed in.

The SimpMessagingTemplate is optimized to supporting using a single
MessageHeaders instance while preparing a message.

This commit also updates code using the SimpMessagingTemplate to take
advantage of its new capabilities.

Issue: SPR-11468
Merge pull request #512 from rstoyanchev/message-headers

Enhance MessageHeaderAccessor support and optimize message creation
Switch BufferingStompDecoder to decoration

The BufferingStompDecoder now decorates rather than extend
StompDecoder. This allows a single StompDecoder instance to be
configured and extended independantly while buffering remains a
separate concern.