Issue: SPR-15149

Issue: SPR-15871

Issue: SPR-15872

Issue: SPR-15869

Issue: SPR-15532

Bean-derived null values may still get passed into bean properties and injection points but only if those are declared as non-required. Note that getBean will never return null; a manual bean.equals(null) / "null".equals(bean.toString()) check identifies expected null values now.  This will only ever happen with custom FactoryBeans or factory methods returning null - and since all common cases are handled by autowiring or bean property values in bean definitions, there should be no need to ever manually check for such a null value received from getBean.

Issue: SPR-15829

Issue: SPR-15149

Refer to both Servlet and reactive stacks in web.adoc
Move web-integration.adoc to the very end
Link in web-flux-functional.adoc
Insert "Spring Web MVC" or "Servlet" prefix in chapter titles

Issue: SPR-15149

Issue: SPR-15869

Includes latest dependency updates (Tomcat 8.5.20, Protobuf 3.4, RxJava 2.1.3, Caffeine 2.5.5)

Issue: SPR-15870

Issue: SPR-15858

Issue: SPR-15542

Issue: SPR-15867

Instead of always using the default JSON mime types

Issue: SPR-15860

Issue: SPR-15852

This commit restores and existing redirectedUrl and forwardedUrl
methods (simple String comparison) and creates separate
redirectedUrlTemplate and forwardedUrlTemplate methods that expand
and also encode before comparing.

Issue: SPR-15834

Issue: SPR-15819

Issue: SPR-15863

Issue: SPR-15814

Issue: SPR-15851

This commit also fixes compilation with JDK9 since
KT-18832 has been fixed.

Issue: SPR-15814

Issue: SPR-15841

Includes latest dependency updates (Hibernate Validator 6.0.1, Caffeine 2.5.4, Netty 4.1.14, Tomcat 8.5.19, Johnzon 1.1.2, JsonPath 2.4, Jython 2.7.1)

Issue: SPR-15839
Issue: SPR-15808

Issue: SPR-15667

Sync 3.1.0.BUILD-SNAPSHOT changes to Operators.checkRequest (removed)

This commit revises the implementation of the SpringExtension to use
the getRequired*() methods in the ExtensionContext which are now built
into JUnit Jupiter thanks to inspiration from the initial "convenience"
methods implemented here.

Issue: SPR-15845
Issue: SPR-15846