Add the Spring IO Platform plugin

INT-3396: Polishing

JIRA: https://jira.spring.io/browse/INT-3396

Updates for latest snapshots of the Spring IO plugin

Update the configuration to use the renamed plugin. Add a dependency in
the springIoVersions configuration that points to the versions published
by Spring IO.

Upgrade to 0.0.3.RELEASE

Upgrade the plugin version to 0.0.3.RELEASE. Only apply the plugin if
the platformVersion property has been set.

Polishing following upgrade to 0.0.3.RELEASE

- Remove reference to snapshot plugins repository
- Remove unnessary use of the springIoVersions configuration

Improve configuration of snapshot repository

Upgrade to latest SD to be consistent with IO
INT-3407: Fix TX-sync-processor potential NPE

JIRA: https://jira.spring.io/browse/INT-3407
INT-3409 Update to Spring AMQP 1.3.3

JIRA: https://jira.spring.io/browse/INT-3409

Stub connection factory API changes.
INT-3410 TCP NIO Deadlock with Bound TE

JIRA: https://jira.spring.io/browse/INT-3410

When running a fixed thread pool with a bound queue,
and CALLER_RUNS execution rejection policy, it
was possible to deadlock the IO selector thread.

Add a `CompositeExecutor` to use different threads for
IO to those used for message assembly.

Add a `CallerBlocksPolicy` to block the invoking thread
(for a specified time) if the pool is exhausted.

Add documentation.

Polishing
INT-3405 JMSCorrelationID* for JMSOutboundGateway

JIRA: https://jira.spring.io/browse/INT-3405

Disallow `JMSCorrelationID*` with reply-container

Polishing; Docs, Test
INT-3408: Fix `IRHolder` TX-sync Inconsistency

JIRA: https://jira.spring.io/browse/INT-3408

* Add `TransactionSynchronizationFactoryBean`
* Introduce `IntegrationResourceHolderSynchronization`
to get deal with `IntegrationResourceHolder` for custom `TransactionSynchronization`
* Encapsulate `IntegrationResourceHolder` in the `DefaultTransactionSynchronizationFactory`
* Get deal with `IntegrationResourceHolder` and bind it to the `TransactionSynchronizationManager`
only if `TransactionSynchronization` from `transactionSynchronizationFactory`
is `synchronization instanceof IntegrationResourceHolderSynchronization`

INT-3408: Encapsulate binding in the `DefTxSyncF`
INT-3386 Improve Aggregator Performance

JIRA: https://jira.spring.io/browse/INT-3386

Eliminate unnecessary group copy during retrieval in the
aggregator. This is expensive with large groups.

Ensure that the reaper uses a snapshot of the group at the
time it is considered for reaping.

AggregatorTests.testAggPerf() -  before:

    AggregatorTests [main] : Sent 0 in 0.0 (10k in 0ms)
    AggregatorTests [main] : Sent 10000 in 4.872 (10k in 4872ms)
    AggregatorTests [main] : Sent 20000 in 16.86 (10k in 11988ms)
    AggregatorTests [main] : Sent 30000 in 36.809 (10k in 19949ms)
    AggregatorTests [main] : Sent 40000 in 65.045 (10k in 28236ms)
    AggregatorTests [main] : Sent 50000 in 100.329 (10k in 35284ms)
    AggregatorTests [main] : Received 60000
    AggregatorTests [main] : Sent 60000 in 143.106 (10k in 42777ms)
    AggregatorTests [main] : Sent 70000 in 147.027 (10k in 3921ms)
    AggregatorTests [main] : Sent 80000 in 158.664 (10k in 11637ms)
    AggregatorTests [main] : Sent 90000 in 177.956 (10k in 19292ms)
    AggregatorTests [main] : Sent 100000 in 205.045 (10k in 27089ms)
    AggregatorTests [main] : Sent 110000 in 240.005 (10k in 34960ms)
    AggregatorTests [main] : Received 60000
    AggregatorTests [main] : Sent 120000 in 282.566 (10k in 42561ms)

After:

    AggregatorTests [main] : Sent 0 in 0.0 (10k in 0ms)
    AggregatorTests [main] : Sent 10000 in 0.612 (10k in 612ms)
    AggregatorTests [main] : Sent 20000 in 0.925 (10k in 313ms)
    AggregatorTests [main] : Sent 30000 in 1.131 (10k in 206ms)
    AggregatorTests [main] : Sent 40000 in 1.288 (10k in 157ms)
    AggregatorTests [main] : Sent 50000 in 1.361 (10k in 73ms)
    AggregatorTests [main] : Received 60000
    AggregatorTests [main] : Sent 60000 in 1.522 (10k in 161ms)
    AggregatorTests [main] : Sent 70000 in 1.619 (10k in 97ms)
    AggregatorTests [main] : Sent 80000 in 1.696 (10k in 77ms)
    AggregatorTests [main] : Sent 90000 in 1.75 (10k in 54ms)
    AggregatorTests [main] : Sent 100000 in 1.81 (10k in 60ms)
    AggregatorTests [main] : Sent 110000 in 1.851 (10k in 41ms)
    AggregatorTests [main] : Received 60000
    AggregatorTests [main] : Sent 120000 in 1.918 (10k in 67ms)