For compatibility with Gradle docbook-reference-plugin, which cannot
handle DocBook 4.

This change eliminates the spring-framework-reference subproject, moving
these sources into the root project's own src directory.

This makes sense because the reference docs span all submodules, and
also because api Javadoc is created at the root project level as well.
This means that both api and reference documentation output will now
reside in the root project's 'build' directory. This is more consistent
and easy to discover.

Prior to change, there were 175 instances of <methodname/> elements
including parentheses (e.g.: <methodname>foo()</methodname>, and
36 instances without.

Now all 211 instances include parentheses for consistency.

* eliminated all usage of "the section entitled", because <xref> links already render including "the section called ".  This was resulting in sentences like 'see also the section entitled the section called "@Autowired"'. This issue affected nearly all sections of the documentation, so went beyond just beans.xml

* fixed table overflow in the "Using filters to customize scanning" section (approx. p.90)

* fixed all code overflows in <programlisting/> elements

* corrected a couple minor syntax errors with SpEL examples (missing closing braces)

* added 'language="..."' element to <programlisting> elements where appropriate to enable syntax highlighting.

* normalized all code indention to four-space (some code listings were using one- and two-space)

* updated all code listings to use same-line opening braces.

* eliminated section regarding backward compatibility with Spring DTDs and singleton=true|false.  This seems like cruft to me, and we shouldn't keep historical notes around forever.

* Added <note> regarding the new thread scope (SimpleThreadScope) to Section 3.5 Bean Scopes.  Also updated the section on registering a custom Scope implementation to use the SimpleThreadScope as an example.

* updated the new-in-3.xml section to improve the @Configuration example

Move classic aop-api chapter to appendix
Move JMS 1.0.2 related documentation to appendix
Remove references to Commons Annotations and source level metadata abstraction
Fix program highlighting issue in beans.xml