Add SimpleMessageConverter
Add new features on @ControllerAdvice

Prior to this commit, @ControllerAdvice annotated beans would
assist all known Controllers, by applying @ExceptionHandler,
@InitBinder, and @ModelAttribute.

This commit updates the @ControllerAdvice annotation,
which accepts now base package names, assignableTypes,
annotations and basePackageClasses.

If attributes are set, only Controllers that match those
selectors will be assisted by the annotated class.
This commit does not change the default behavior when
no value is set, i.e. @ControllerAdvice().

Issue: SPR-10222
Polish ControllerAdvice selectors

Issue: SPR-10222
Merge pull request #380 from bclozel/SPR-10222
Allow TypeDescriptor create with null generics

Restore the ability to create a TypeDescriptor for a collection or
map where the generics may be null.

Issue: SPR-11006
Upgrade json-path to 0.9.0 version

This version fixed bugs and improved performance.
New features: "select multiple attributes" and
"Array operations and slicing improved" (a new example
has been added in tests to reflect that).

See https://github.com/jayway/JsonPath/blob/master/README

Issue: SPR-10990
Support @PathVariable in annotated message handling methods

Prior to this commit, @SubscribeEvent @UnsubscribeEvent and
@MessageMapping annotated message handling methods
could only match a strict message destination.

This commit adds a @PathVariable annotation and
updates the message matching/handling process, since
message handling methods can now match PathMatcher-like
destinations and get path variables injected in parameters.

Issue: SPR-10949
Polish AnnotationMethodMessageHandler and annotations
Remove @UnsubscribeEvent

The STOMP UNSUBSCRIBE message does not have a destination header so
there is no obvious simple way to do a mapping and the need for it
is not clear yet.
Improve GenericMessage.toString()

Restore pringing the payload first and headers second as it has been in
SI but also handle specifically the case where the body is a byte array
to minimize unnecessary "noise" that causes otherwise for STOMP msgs.