INT-2943: Retry: Don't Wrap in MessagingException

Previously, `RequestHandlerRetryAdvice` wrapped a Handler's (business) Exceptions in a
`MessagingException` on each retry within `RetryCallback#doWithRetry`
and before `RetryPolicy#canRetry`.
It made useless some retry framework out-of-the-box features like `BinaryExceptionClassifier`

* Push wrapping to `MessagingException` after `retryTemplate#execute`
* Polishing `ErrorMessageSendingRecoverer` regarding new logic
* Add `retryableExceptions` test

You can now properly specify Business exceptions with the retry policy to
perform conditional retry.

JIRA: https://jira.springsource.org/browse/INT-2943

Polishing

Only wrap Throwable in ThrowableHolderException if the Throwable
is not an Exception.

INT-2943: Polishing ErrorMessageSendingRecoverer
INT-2998: Channel Adapters' Lifecycle Refactoring

* Add XSD attributeGroup `smartLifeCycleAttributeGroup`
* Use it for all adapters tags
* Refactoring `AbstractChannelAdapterParser` hierarchy
* Refactoring some `MessageHandler`'s that should not have `autoStartup` & `phase`.
    It is the responsibility of `AbstrctEndpoint`
* Polishing some tests according new logic

JIRA: https://jira.springsource.org/browse/INT-2998

INT-2998: Polishing

Polishing

 - Reformat schemas where indentation changed
 - Add SLC to the UDP inbound adapter
INT-3027: Headers Enrichment for <enricher>

* Add `<header>` sub-element to `<enricher>`
* Refactoring to `EnricherParser`
* Add Headers Enrichment logic to `ContentEnricher`
* Add tests
* What's new and Content Enricher's `<header>` note

JIRA: https://jira.springsource.org/browse/INT-3027
INT-3027: Addressing PR comments
INT-3027: add NPE asserts to map properties
INT-3027: add overwrite & type to enricher header

Move `HeaderValueMessageProcessor` hierarchy to 'transformer.support' package
INT-3027: Make header's overwrite=true by default