Closes gh-3643

Closes gh-3652

Closes gh-2671

This commit adds a new property, logging.exception-conversion-word,
that can be used to configure the conversion word that is used when
logging exceptions. The default value, %rEx, will log exceptions
with the root cause first and include class packaging information in
the stack trace. The new property is supported when using either
Logback or Log4J2.

Closes gh-3684

Upgrade documentation for the `hal` and `links` endpoints as they are
not using the root anymore.

Closes gh-3621

Update LinksMvcEndpoint and HalBrowserMvcEndpoint so that no longer try
to use the `/` context path. Links are now available from `/links` and
the HAL browser is available from `/hal`.

The actuator HAL browser now works with either WebJars or the Spring
Data version. It also now transforms the initial HTML so that the
form is pre-populated with `/links`.

When using Spring Data's HAL browser, the root includes a link to
`/links` with a rel of `actuator`.

See gh-3621

Replace `Link :` prefixes in the restdoc headings with link icons next
to the HTTP request. This fixes render issues with the titles and allows
the TOC to still function correctly.

Fixes gh-3689

Update `spring-boot-actuator-docs` to generate rest documentation in
the compile phase.

Add a new `@ImportAutoConfiguration` annotation that can be used by
tests that wish to selectively import certain auto-configuration
classes. Also add `@AutoConfigurationPackage` so that package
registration is decoupled from `@EnableAutoConfiguration`.

An added benefit of the change is @EnableAutoConfigurationImportSelector
can now be subclassed to provide custom annotation support if needed.

Fixes gh-3660
See gh-2772

Revert commit 1d31d23e to
remove `include` from `@EnableAutoConfiguration`. We'll
add a dedicated annotation instead to fix this.

See gh-3660

This reverts commit f7619706.

See gh-3569

This commit updates the default logging configuration for both Logback
and Log4J 2 to include class packaging information when logging
exceptions and to log the root cause first.

Closes gh-3398
Closes gh-3399

Closes gh-3569

Closes gh-3675

Closes gh-3676

Closes gh-3677

Closes gh-3678

Closes gh-3679

Closes gh-3680

Closes gh-3682

Closes gh-3683

Closes gh-3681

Closes gh-3674

Closes gh-3673

Closes gh-3672

Closes gh-3671

Closes gh-3670

Closes gh-3669

This commit updates the default output produced when using Log2J 2 to
be similar to the output produced by Logback. It introduces a new
converter for throwables that adds some whitespace around stacktraces
and a color converter that produces ANSI-colored output when enabled
via spring.output.ansi.enabled.

Closes gh-3548

Spring Framework 4.2 introduced support for before modes in
`@DirtiesContext` Make sure that `@IntegrationTest` also support
these new modes.

Closes gh-3642

Explicitly mention that `spring.data.mongodb.uri` can be used to
customize additional settings such as replica set.

Closes gh-2624

* pr/3667:
  Polish Javadoc

Closes gh-3667