Delete accidental call to System.err
Re-enable OpenJPA + AspectJ tests

With the upgrade to JDK 8, the OpenJPA/AspectJ integration tests now
pass again. Thus, we are re-enabling these tests.

Issue: SPR-10333
Add TODO for fate of Hibernate JPA integration tests

Issue: SPR-11922
AsyncExecutionInterceptor uses submitListenable if method signature indicates ListenableFuture

Issue: SPR-11909
MBeanExporter implements DisposableBean again (also revised logging and rearranged properties)

Issue: SPR-8045
Polishing
Add check for unused WebSocket sessions

Sessions connected to a STOMP endpoint are expected to receive some
client messages. Having received none after successfully connecting
could be an indication of proxy or network issue. This change adds
periodic checks to see if we have not received any messages on a
session which is an indication the session isn't going anywhere
most likely due to a proxy issue (or unreliable network) and close
those sessions.

Issue: SPR-11884
Improve JettySockJsIntegrationTests to show real error

In a recent CI build failure a test timed out waiting for a message:
https://build.spring.io/browse/SPR-PUB-1316

In fact there was a WebSocket transport failure originating in Jetty's
WebSocket Parser. However this failure is only apparent by looking at
the logs. This change adds a check if a transport error ocurred while
we were waiting and throws an AssertionError.
DefaultAdvisorChainFactory never passes null into ClassFilter, enabling async advisor to work without target class as well

Issue: SPR-11910
Polishing

Issue: SPR-11910
Support for nested path using field access

This commit adds a nested path support for DirectFieldAccessor that is
similar to what BeanWrapper provides. It is now possible to use
expressions such as "person.address.city.name" to access the name of
the city that a given person lives in using fields to traverse the
graph.

DirectFieldAccessor also now supports an auto-grow option to create
a default instance for a "null" intermediate path. This option is
false by default and leads to a NullValueInNestedPathException in such
a case.

This commit also harmonizes part of the tests suite so that core tests
are shared between BeanWrapperImpl and DirectFieldAccessor.

Note that map and list access is not implemented as part of this
commit.

Issue: SPR-9705
Workaround for WFLY-3474 NullPointerException

Prior to this commit, the ServletResponseHttpHeaders.get method
would throw an NPE when used under Wildfly 8.0.0.Final and 8.1.0.Final.
This can be traced to WFLY-3474, which throws an NPE when calling
HttpServletResponse.getHeaders("foo") and that header has not
been defined prior to that.
This would cause NPE being thrown by AbstractSockJsService when
checking for CORS HTTP headers in the server HTTP response.

This commit surrounds that method call in AbstractSockJsService and
guards against this issue.

Issue: SPR-11919