Issue: SPR-12970
Issue: SPR-13285

In addition to specifying the event type to listen to via a method
parameter, any @EventListener annotated method can now alternatively
define the event type(s) to listen to via the "classes" attributes (that
is aliased to "value").

Something like

@EventListener({FooEvent.class, BarEvent.class})
public void handleFooBar() { .... }

Issue: SPR-13156

Issue: SPR-7301

Also includes an explicit note on stop vs destroy callbacks for Lifecycle beans.

Issue: SPR-13118
Issue: SPR-12882
Issue: SPR-12345
Issue: SPR-11671

Issue: SPR-13041

Issue: SPR-13069

Issue: SPR-13108

Issue: SPR-12702

Issue: SPR-13038

Issue: SPR-13000

Issue: SPR-12855

Various documentation improvements related to `@Configuration` and
`Bean`. Better describe how method parameter can be used to declare
dependencies of a particular bean. Also add an explicit mentions related
to "hard-wiring" of dependencies in configuration classes.

Issue: SPR-12773

The upgrade to a more recent asciidoc format led to a bunch of of
broken Admonition as the text block now requires four equal signs while
previous versions tolerated only 3.

Issue: SPR-12791

Core and Web chapters are important chapters in the Spring Framework
reference documentation, and splitting them in multiple files will
help to evolve the documentation while not creating too many files.

Issue: SPR-12309

The reference documentation is now organized in asciidoc bookparts.
Bookparts sections can be also put in separate files, when their
size and theme are important enough to justify that.

Documentation Layout:
```
index
  |-- overview
  |
  |-- whats-new
  |
  |-- core
  |   |-- core-beans
  |   |-- core-aop
  |-- testing
  |
  |-- data-access
  |
  |-- web
  |   |-- web-mvc
  |   |-- web-view
  |-- integration
  |
  |-- appendix
      |-- appx-spring-tld
      |-- appx-spring-form-tld
```

Supersedes and closes #641

Issue: SPR-12309