INT-2935: Improve Event Inbound Adapter

Previously, the `ApplicationEventListeningMessageProducer` accepted
all `ApplicationEvent`'s and than filtered them.
This caused some `ApplicationEventMulticaster.retrieverCache` overhead.

* Improve `ApplicationEventListeningMessageProducer` to `implements SmartApplicationListener`.

    This allows filtering earlier on first the appropriate `ApplicationEvent`
    using `ApplicationEventListeningMessageProducer#supportsEventType`
    and caching the `ApplicationListener` only for that `ApplicationEvent`.

* Re-register `ApplicationEventListeningMessageProducer` in the `ApplicationEventMulticaster`
    when  `ApplicationEventListeningMessageProducer#setEventTypes` is invoked
    to clear the `ApplicationEventMulticaster.retrieverCache`.

* Move `org.springframework.integration.gemfire.inbound.SpelMessageProducerSupport` to core `ExpressionMessageProducerSupport`.

* Add test for the new logic int `ApplicationEventListeningMessageProducer` and its behavior with respect to the `ApplicationEventMulticaster.retrieverCache`.

JIRA: https://jira.springsource.org/browse/INT-2935

INT-2935: EMPS JavaDoc & AELMP ReadWriteLock

INT-2935: AELMP#eventTypes changing 'barrier'

INT-2935: avoid 'eventTypes' mutation afterwards

INT-2935: Polishing according PR comments

INT-2935: Fix NPE in the `setEventTypes`

Minor Polishing

   Polish java docs/comments
   Remove compiler warnings
Merge pull request #750 from artembilan/INT-2935

* INT-2935:
  INT-2935: Improve Event Inbound Adapter
INT-2822: 'requires-reply' for outbound gateways

* Add `requires-reply` attribute for all adapters outbound gateways as `true` by default
* WS-outbound-gateway is still without it, because it has its own specific attribute `ignore-empty-responses`
* Make `requires-reply` as `false` by default for `jdbc:stored-proc-outbound-gateway` inasmuch as `jdbc:stored-proc-outbound-adapter`
doesn't have ability to configure `returning-resultset`
* add parser tests for `requires-reply`

JIRA: https://jira.springsource.org/browse/INT-2822
INT-2822 'requires-reply' for ws:outbound-gateway
INT-2822: Polishing after rebase
INT-2822: deprecate 'ignore-empty-responses'

* Add 'requires-reply' section into What's New