INT-1362-2: Reset RequestContextHolder in Tests

JIRA: https://jira.springsource.org/browse/INT-1362
INT-3181: Improve JdbcChannelMS usingIdCache doc

JIRA: https://jira.springsource.org/browse/INT-3181

INT-3181: Fix JdbcChannelMS#pollMessageFromGroup

* Add `doRemoveMessageFromGroup` and check its result.
If it is `false` then just return `null`, not polled `Message`
* Add `AbstractTxTimeoutMessageStoreTests#testInt3181ConcurrentPolling` test
and implement it for some DBs
* Make a note regarding MVCC as important in the Doc

Minor Polishing
INT-3185 Fix Direct Handlers When Exposed as MBean

When determining candidates for direct invocation, we need
to use the target of any existing proxy (such as JMX Metrics).

Copy ServiceActivatorDefaultFrameworkMethodTests to the JMX project
and adjust to work with JMX Proxies.

INT-3185: fix for AbstractSMHFBean#checkReuse

JIRA: https://jira.springsource.org/browse/INT-3185
INT-2664: (S)FTP Inbound: Preserve File Timestamp

JIRA: https://jira.springsource.org/browse/INT-2664

INT-2664: add `preserve-timestamp` attribute

Doc Polishing
Test Case Fixes for Latest SPR 4 Snapshot

- Close child context before parent to publish child close event to parent
- SpelRouter FB injection
- Don't pass null Method to TransactionAttributeSource.getTransactionAttribute()
INT-3186 Fix Metrics For Direct MessageHandler

When a simple MessageHandler is referenced from a
`<service-activator/>`, it is wrapped in an anonymous
AbstractReplyProducingMessageHandler to facilitate proper handling of
the `<request-handler-advice-chain/>` and so that normal
'produced no reply` messages are logged.

Previously, this caused 2 MBeans to be exposed, one for tha actual
handler; one for the wrapper.

This added more stack frames between the dispatcher and the
handler (because 2 sets of statistics were captured).

The root cause was that the MBean exporter was not aware of the
relationship between these objects.

https://jira.springsource.org/browse/INT-3186

Add code to the IntegrationMBeanExporter to suppress adding
metrics to the wrapper.

This involves detecting that it is a wrapper and not exposing
it as an MBean and, when matching handlers with endpoints,
checking that the wrapped handler is the actual handler for the endpoint.

Update test to reflect the reduced number of stack frames between
the dispatcher and handler.

Also add tests to verify the detection of multiple references to
the same ARPMH.

INT-3186: `IntegrationMBeanExporter` optimization
INT-3182 Fix JMX Operation Invoking With Primitive

Previously, methods with primitive parameters were not matched
with primitive wrapper objects.

Check, if the argument is a primitive wrapper, that the paramer type
can be the equivalent primitive.

Add test case.

INT-3182 Polishing - PR Comments

Extract PrimitiveWrapper->Primitive map to ClassUtils.

JIRA: https://jira.springsource.org/browse/INT-3182