INT-2882 Upgrade DocBook Reference Plugin to 0.2.6

For reference see: https://jira.springsource.org/browse/INT-2882

* Verify spacing
* Ensure all source code samples are typed: e.g. <programlisting language="xml">
* Ensure source code fits space in PDF format
Merge pull request #707 from ghillert/INT-2882
INT-2958: XSD: move 'charset' from common attrs

`charset` for `<object-to-string-transformer>` was placed in the common `inputOutputChannelGroup` attributeGroup.
`charset` wasn't available  within `<chain>`.

* Move 'charset' from `inputOutputChannelGroup` to the new `specialized-transformer-charset-aware-type` complexType
* Add test for 'charset' within `<chain>`

JIRA: https://jira.springsource.org/browse/INT-2958
Merge pull request #764 from artembilan/INT-2958
INT-2957 Remove Unnecessary AspectJ Dependencies

Core, JDBC, JMX, JPA each had dependencies for both
weaver and rt jars. weaver is a superset of rt.

Remove dependencies on the rt jar.

Further JDBC, JPA have no dependencies on AspectJ.

Finally, the JMX dependency was compile, when only
testCompile is needed.
Merge pull request #765 from garyrussell/INT-2957

* garyrussell-INT-2957:
  INT-2957 Remove Unnecessary AspectJ Dependencies
INT-2531: Remove deprecations in XML Adapter after upgrade to Spring 3.1.1

* BeanDefinitionParserDelegate constructor now prefers an Environment. Circumvent this
preference by directly getting BeanDefinitionParserDelegate from the associated ParserContext
Merge pull request #759 from sobychacko/INT-2531

* sobychacko-INT-2531:
  INT-2531: Remove deprecations in XML Adapter after upgrade to Spring 3.1.1
INT-2960 - Remove deprecated 'xpath-selector'

For reference see: https://jira.springsource.org/browse/INT-2960

* Remove 'xpath-selector' from XML Schema
* Remove parser class
* Remove tests
* Remove respective reference documentation
Merge pull request #767 from ghillert/INT-2960
INT-2755: Support 'id' for <chain> sub-components

* Introduce XSD 'id' attribute for all `<chain>` sub-components
* Register `<chain>` sub-components as Beans with names based on `<chain>` 'id'
* Generate aliases for sub-components based on element 'id'
* Add `<chain>` parser test to check sub-components as Beans within `BeanFactory`
* Ignore `NestedChainParserTests` as abnormal and confused for SI-configs
* Now `<chain>` sub-components are trackable by `MessageHistory`
* Now `<chain>` sub-components are eligible for JMX export
* Polishing some failed tests

https://jira.springsource.org/browse/INT-2755
https://jira.springsource.org/browse/INT-2321
INT-2755: Register as Beans only if 'id' provided