INT-3314: Fix BeanFactory Population for `SAH`

JIRA: https://jira.springsource.org/browse/INT-3314

Add to `ServiceActivatingHandler` `beanFactory` population code for the `MessageProcessor` delegate

INT-3314: Populate `BF` to `HValueMProcessor`s

Make `XPathExpressionEvaluatingHeaderValueMessageProcessor` as `public`

INT-3314: Populate `BF` to `HE.messageProcessor`

INT-3314: Add `BF` `NPE` protection

INT-3314 XPath Header Enricher Test

Add a test that verifies the `BeanFactoryTypeConverter` is used
(convert to a TimeZone object).
INT-3316 BeanFactoryTypeConverter Concurrency

JIRA: https://jira.spring.io/browse/INT-3316

The `SimpleTypeConverter` delegate uses property editors
which are not thread safe. We protect against concurrent
access when the source is not a String, but when a String,
we delegate to the `STC`.

Synchronize access to the `STC.convertIfNecessary()` method.