Create a new spring-boot-antlib module which allows Apache Ant users
to easily create executable jars.

Fixes gh-3339

* pr/3341:
  Cleanup logging so execution order is unimportant

Fixes gh-3341

Update AbstractLoggingSystemTests to use a TemporaryFolder rule.

Fixes gh-3349

Rename the `html5AppCache` property from `ResourceProperties.Chain` to
`html-application-cache`.

Fixes gh-3354

By default, Jetty uses a singleton shutdown thread, registered as a
shutdown hook, to stop its components. This single thread breaks the
restart logic in devtools as a second restart causes a second attempt to
start the singleton shutdown thread which fails with an
IllegalStateException. This processing is unnecessary in a Spring Boot
application as the application context’s lifecycle when ensure that
Jetty is shutdown.

This commit updates the embedded Jetty container to remove its
components from Jetty’s shutdown thread. This leaves the thread with
no components to manage at which point it removes its registration as a
shutdown hook.

Closes gh-3343

Closes gh-3325

Closes gh-3296

See gh-3296

* pr/3346:
  Polish

Closes gh-3346

Fixes gh-2816

* pr/3344:
  Polish doc

Closes gh-3344

* pr/3123:
  Polish
  Improve Spring Resource Handling support

Polish resource handling chain support. Make sure that the chain is
enabled automatically if at least one strategy is enabled.

See gh-1604

This commit improves support of the Resource Handling features
introduced in Spring Framework 4.1. Those features add new ways to
resolve and transform static resources in applications.
See [this blog
post](https://spring.io/blog/2014/07/24/spring-framework-4-1-handling-static-web-resources)
for more details.

The `ResourceUrlEncodinFilter` is added for compatible template engines:
Velocity and Thymeleaf. It assists them with rewriting the URLs of
static resources when rendering templates.

New keys are added in the `ResourceProperties` in order to configure
the Resource Handling chain. `ResourceResolvers` and
`ResourceTransformers` are registered accordingly in
`WebMvcAutoConfiguration`.

Here is an example of enabling a `ContentVersionStrategy` on all
static resources, meaning their names will be changed for cache
busting purposes by adding a content hash at the end of the file name.
Like "/js/jquery.js -> /js/jquery-872ca6a9fdda9e2c1516a84cff5c3bc6.js".

```
spring.resources.chain.enabled:true
spring.resources.chain.strategy.content.enabled:true
spring.resources.chain.strategy.content.paths:/**
```

Closes gh-1604
Closes gh-3123

* pr/2713:
  Fix logout in sample secure web applications

Fixes gh-1536

Update logging documentation to show the new `-spring` convention and
the Logback extensions.

See gh-1788
See gh-2558
See gh-3338

Include support for a new <springProperty> element which can be used in
`logback-spring.xml` files to add properties from the Spring
Environment. For example:

	<configuration>
		...
		<springProperty name="destination" source="my.loggger.extradest"/>
		<appender name="FILE" class="ch.qos.logback.core.FileAppender">
			<file>${destination}</file>
				...
			</file>
		</appender>
		...
	</configuration>

Fixes gh-1788

Include support for a new <springProfile> element which can be used in
`logback-spring.xml` files to selectively enable or disable parts of the
configuration. For example:

	<configuration>
		...
		<springProfile name="staging">
			<logger name="sample.logback" level="TRACE" />
		</springProfile>
		...
	</configuration>

Fixes gh-3338

Add a logback sample application to demonstrate how `logback-spring.xml`
can be used for customization.

See gh-2558

Update AbstractLoggingSystem to support convention based logging
configuration specifically for Spring applications. Configurations with
the `-spring` suffix will now be loaded automatically (for example
`logback-spring.xml`).

This change allows for custom log configurations without needing to
reinitialize the logging system. When standard configurations are used
there is no way to prevent early initialization.

Fixes gh-2558

The default is now to reveal all details unless sensitive=true
(instead of only revealing then if sensitive was explicitly false).
The definition of "secure" also changes to something more sensible
where it is only true if security is enabled.

Fixes gh-2816

The default should be to generate a key from the prefix. Otherwise
if user sets the prefix and not the key it can pick up metrics from
another repository (which is what happens in the tests).

* pr/3335:
  Remove unnecessary import
  Remove unnecessary `@After` callback

See gh-3335

`@After` callback was trying to remove the wrong file anyway. This is
now taken care of by the `TemporaryFolder` rule.

Closes gh-3335

* pr/3333:
  Fix typo

Closes gh-3333

Update LogbackLoggingSystem to include status errors in the exception
rather than using `System.err`. Also perform additional cleanup in an
attempt to fix CI build failures.

Fixes gh-3309