INT-3183 Document the IMBE 'id' Attribute

When declaring an IntegrationMBeanExporter, use an 'id' attribute
if you wish to obtain programmatic access to it (using injection
or referencing the BeanFactory.

JIRA: https://jira.springsource.org/browse/INT-3183

Also turn off debug logging for JMX test cases.
INT-3175 Add Caution About Apache HTTP Client

JIRA: https://jira.springsource.org/browse/INT-3175