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

The PathPattern compareTo method is now consistent with equals when
two patterns are of the same specificity but otherwise different.

Separately PathPattern now exposes a Comparator by specificity that
offers the current functionality of compareTo. This can be used for
actual sorting where we only care about specificity.

Consistent behavior with matches(PathContainer), the two had slightly
different logic for handling of empty paths.

Make matchAndExtract independantly usable without the need to call
matches(PathContainer) first. Essentially no longer raising ISE if the
pattern doesn't match but simply returning null.

Rename getPathRemaining to matchStartOfPath since the method does
match and to be more clear about what the method and the return value
intuitively follows.

Remove matchStart which matches the start of the pattern (rather than
the start of the path). It is a use case that does not come up in
request mapping.

Updates to Javadoc
Consistent and separator type neutral naming for trailing slash
PathPattern extracts options from the parser instance

This commit changes the WebClient so that it now throws a
`WebClientResponseException` for `ResponseSpec.bodyTo`. This newly
introduces exception contains the status code, headers, and body of the
response message.

As a consequence of the above, we had to change `onStatus` so that the
`exceptionFunction` now returns a `Mono<Throwable>` rather than a
`Throwable`, which it was before. The Mono allows for asynchronous
operations, such as reading the contents of the body.

Issue: SPR-15824

Remove the separator constructor argument (but preserve internal
functionality) now that PathPatternParser is more explicitly purposed
for URL paths and in any case the use of an alternate separator would
also requires a similar input option on the PathContainer parsing side.

Emphasize specific purpose for URL path matching.