INT-3528 Use Collections min and max methods where appropriate

JIRA: https://jira.spring.io/browse/INT-3528

Use `min` and `max` methods instead of sorting an entire collection to get the minimum or maximum element.

Change other inline `Comparator<?>`s to the `final` fields
INT-3512: Add `<advice-chain>` to the Aggregator

JIRA: https://jira.spring.io/browse/INT-3512

INT-3512: Fix typos

INT-3512: add `expire-` prefix to the advice sub-elements

INT-3512: Mark `AggregatorWithCustomReleaseStrategyTests` as `LONG_RUNNING_TEST`

Doc Polishing
INT-3527: WebSocket and 'o-c-a' Improvements

JIRA: https://jira.spring.io/browse/INT-3527

* `WebSocketInboundChannelAdapter` now handles `CONNECT` STOMP message and sends `CONNECT_ACK` message to the `WebSocketSession` immediately
* `ExpressionMessageProducerSupport` implementations now checks the result of `expression` and if it is a `Message<?>` it is sent to channel without creating a new one
which previously wrapped that `Message<?>` as the `payload`.
* Add `<script>` support to the `<outbound-channel-adapter>`
* Upgrade to the SF 4.1.1
* Add appropriate notes to the Docs
Merge branch 'INT-3528'