INT-3379 - Allow Placeholders for Enums

JIRA: https://jira.spring.io/browse/INT-3379

Change enumerated attributes to a union with xsd:string
to allow placeholders.

JMS and XML deferred to 4.1 due to the amount of
changes needed to the parsers. See INT-3384.
Update tests to be compatible with Spring Web Services 2.2

Spring Web Services 2.2 added a new method, afterCompletion, to
ClientInterceptor. To allow Spring Integration's tests to be run
successfully against Spring Web Services 2.2, this commit adds empty
implementations of this method to two test implementations of the
interface.
INT-3311,INT-3377: Update Spring-* Dependencies

JIRA: https://jira.spring.io/browse/INT-3377
      https://jira.spring.io/browse/INT-3311

Resolve SD-Mongo deprecations
INT-3385 AMQP Support MANUAL Ack Mode

JIRA:https://jira.spring.io/browse/INT-3385

MANUAL was supported in the schema, but there was no
mechanism for the application to ack.

Polishing

- Fix tests
- Add integration test
- More documentation
INT-3065: Add `tweet-data-expression` for Update

JIRA: https://jira.spring.io/browse/INT-3065

Improve `TwitterSearchOutboundGateway` to use an expression
to build the tweet instead of just using the payload (which
remains the default).
INT-3376 Support Meta-Annotation Att. Override

JIRA: https://jira.spring.io/browse/INT-3376

Allow user annotations with Messaging Meta-Annotations
override/supplement attributes set on the meta-Annotation.

PR Comments and More

- Do not create a bean definition for the annotation (interface)
when `MessagingGateway` is used as a meta-Annotation.
- For a `MessagingGateway` restore attributes overridden with empty values
- Other PR comments.

Fully support meta-Annotation hierarchy.

Polishing:

* Upgrade JRuby to 1.7.12
* Replace `AnnotationFinder` with moving its methods to `MessagingAnnotationUtils`
* Refactor aggregator classes to use `MessagingAnnotationUtils` to determine the method for annotation
* Fix `IntegrationComponentScanRegistrar` to skip annotation classes
* Fix `MessagingGatewayRegistrar#replaceEmptyOverrides`
* Improve `MessagingAnnotationPostProcessor` to use `ReflectionUtils.USER_DECLARED_METHODS` `MethodFilter`
* Change the `MethodAnnotationPostProcessor` hierarchy to use just list of annotations to process attributes
INT-2464: Add Mapping Method Args Examples to Docs

JIRA: https://jira.spring.io/browse/INT-2464

INT-2464 Doc Polishing
INT-2879: JPA Retrieving: Add `id-expression`

JIRA: https://jira.spring.io/browse/INT-2879

* Add `id-expression` attribute for the `<int-jpa:retrieving-outbound-gateway>`
* Make it mutually exclusive with other `SELECT` attributes
* Remove deprecated `max-number-of-results`

INT-2879 Polishing

- Improve parser error message.
- Minor doc polish.

INT-2879: Support `delete-after-poll` and `flush`
INT-3378 Bump Spring-AMQP to 1.3.2

JIRA: https://jira.spring.io/browse/INT-3378

Adds a default error handler that rejects messages that
can't be converted and would cause an infinite loop.
INT-3382 Support Easier Aggregator Extensions

JIRA: https://jira.spring.io/browse/INT-3382

- Make private methods protected; add protected getters
- Support obtaining just metadata from stores
- Support just fetching the first message from a group
- add metaSize() to message group

INT-3382: Polishing
INT-3389 GemFire i-c-a `expression` Docbook

JIRA: https://jira.spring.io/browse/INT-3389
INT-3380 Add `@Bean`'s `@BridgeTo`, `@BridgeFrom`

JIRA: https://jira.spring.io/browse/INT-3380

INT-3380: Polishing

INT-3380: Refactoring

Minor JavaDoc Polishing