Remove assertion making locations mandatory

This change finishes work started in SPR-12133.

Issue: SPR-12133
List all spring-framework artifacts in Modules

This change adds the artifacts names in the Spring Framework Modules
documentation. Linking both concepts make it easier to decide which
Spring module should be importer in an application's build.

Issue: SPR-11534
Add Web Improvements to what's new in Spring 4.1 section
Update Javadoc in SimpMessageSendingOperations

Issue: SPR-12143
ConfigurationClassParser checks REGISTER_BEAN conditions before processing configuration class imports

Issue: SPR-12128
AbstractAutowireCapableBeanFactory calls postProcessBeforeInstantiation with fully resolved target type

Issue: SPR-12140
Issue: SPR-12142
LazyInitTargetSource works for @Bean targets as well

Issue: SPR-10508
Issue: SPR-8080
ExtendedBeanInfo uses explicit hashCode calculation (as defensive measure against JDK PropertyDescriptor changes)
Polishing
Polish recent changes to reference manual
AbstractAutowireCapableBeanFactory avoids early FactoryBean instantiation on currently created configuration bean

Issue: SPR-12141
Polishing
Documentation updates describing SpEL compiler usage
Prevent incorrect ImportAware metdata injection

Update ImportRegistry to track all import registrations that occur
against an importing class (rather than just keeping the last). In
addition, prune imported classes from the registry when a configuration
class is removed during the REGISTER_BEAN ConfigurationPhase.

This update prevents incorrect metadata from being injected into an
ImportAware class which is imported twice by different configurations
classes (when one of the configuration classes will be ultimately skipped
due to a @Condition).

Issue: SPR-12128
Update the what's new section
Add mention of ResponseBodyAdvice
Add section on building controller links from views
Update reference documentation for JSONP support

Issue: SPR-12113
Transform absolute links in ResourceTransformers

Prior to this change, ResourceTransformers that transformed resources by
updating the links to other resources, worked only if links were
relative to the resource being transformed.
For example, when the CssLinkResourceTransformer rewrote links within
a "main.css" resource, only links such as "../css/other.css" were
rewritten.

Using relative links is a recommended approach, because it's totally
independent from the application servlet path, context path, mappings...

This change allows absolute links to be rewritten by those Transformers,
provided those links are accurate and point to existing resources.

Issue: SPR-12137
ImportRegistry as a package-visible top-level interface which can easily be shared within the package

Issue: SPR-12128