Switch implementations of ApplicationListener<ContextRefreshEvent> for
SmartInitializingSingleton when possible.

Fixes gh-1939

Closes gh-1779

See gh-1779

Accidentally committed in 4668f597

See gh-1950

* ssl-keystore-classpath-test:
  Add Jetty SSL keystore in classpath test

Update JettyEmbeddedServletContainerFactoryTests to test loading an
SSL keystore from the classpath. Currently this is a Jetty only feature,
although if https://issues.apache.org/bugzilla/show_bug.cgi?id=56777 is
fixed we could do the same thing with Tomcat.

Closes gh-1943

Fixes gh-1948

Update RelaxedConversionService to support more relaxed enum binding.

Fixes gh-1950

Previously, HypermediaAutoConfiguration would trigger the creation of
an ObjectMapper bean named _halObjectMapper. This bean did not have the
spring.jackson.* configuration applied to it, however its presence
would revent JacksonAutoConfiguration from creating its
ObjectMapper. This left the user with an ObjectMapper that did not
honour the spring.jackson.* configuration.

This commit updates HypermediaAutoConfiguration to use the
Jackson2ObjectMapperBuilder that may have been created by
JacksonAutoConfiguration. If the builder exists it is used to configure
the _halObjectMapper bean.

Fixes gh-1949

The http.mappers.* configuration properties assumed that the mapping
was JSON (on of the property names was jsonPrettyPrint) and also only
exposed a small subset of the configuration options supported by
Jackson (and GSON). The property names implied that it would configure
all HTTP mapping, however it was ignored by GsonAutoConfiguration.

This commit deprecates the support for http.mappers.* in favour of
configuring Jackson or Gson instead. Jackson can be configured
declaratively using the spring.jackson.* properties or programtically.
Gson can be configured programatically by using a GsonBuilder to
create a Gson instance with the desired configuration.
gh-1946 has been opened to add support for declarative configuration
of Gson.

Closes gh-1945

Closes gh-1919

Previously, only the http.mappers.json-sort-keys property was applied
by JacksonAutoConfiguration. This commit updates it to also apply the
http.mappers.json-pretty-print property as well.

See #1919

Closes gh-1923

See gh-1923

Conflicts:
	spring-boot-dependencies/pom.xml

Closes gh-1936

Closes gh-1906

Closes gh-1905

Fixes gh-1944

Previously, for a non-async response with a successful status (< 400),
ErrorPageFilter would always call flushBuffer. This triggers an
exception in Tomcat if the client has closed the connection before the
response has been fully sent. In this case, Tomcat treats the response
as successful and commits it before control returns to the filter.

This commit updates ErrorPageFilter to only perform the flush if the
response has not already been committed, leaving any further flushing
that may be necessary to be handled by the servlet container.

Fixes gh-1938

Update ConfigurationPropertiesReportEndpoint to find
@ConfigurationProperties using `context.findAnnotationOnBean` rather
than `AnnotationUtils.findAnnotation`. This will correctly find the
annotation even if the bean is an interface based proxy.

Fixes gh-1927

Switch from external docbook XSLT to those shipped as part of the
Maven plugin.

Fixes gh-1942

Previously, configuration of a ServletContext init parameter required
the use of a ServletContextInitializer bean. This commmit adds
support for declarative configuration via the environment using
server.context_parameters.<name>=<value>.

Closes gh-1791

Add a 'module' layout for the repackager which includes all 'compile'
and 'runtime' scope dependencies and does not require a main class.

Fixes gh-1941

ServerConnector is in different packages in Jetty 8 and Jetty 9 which
was leading to a NoClassDefFounderError when SSL was used with
Jetty 8.

This commit updates SslServerConnectorFactory to return an
AbstractConnector, a super class of ServerConnector, that is in the
same package in both Jetty 8 and Jetty 9. This class does not provide
a setPort method so the setting of the port has been pushed down into
the SslServerConnectorFactory implementation.

SSL samples for both Jetty 8 and Jetty 9 have been added to verify
SSL with both supported versions of Jetty.

Closes gh-1925

Closes gh-1897