This commit introduces support for CORS in Spring Framework.

Cross-origin resource sharing (CORS) is a mechanism that allows
many resources (e.g. fonts, JavaScript, etc.) on a web page to
be requested from another domain outside the domain from which
the resource originated. It is defined by the CORS W3C
recommandation (http://www.w3.org/TR/cors/).

A new annotation @CrossOrigin allows to enable CORS support
on Controller type or method level. By default all origins
("*") are allowed.

@RestController
public class SampleController {

	@CrossOrigin
	@RequestMapping("/foo")
	public String foo() {
		// ...
	}
}

Various @CrossOrigin attributes allow to customize the CORS configuration.

@RestController
public class SampleController {

	@CrossOrigin(origin = { "http://site1.com", "http://site2.com" },
				 allowedHeaders = { "header1", "header2" },
				 exposedHeaders = { "header1", "header2" },
				 method = RequestMethod.DELETE,
				 maxAge = 123, allowCredentials = "true")
	@RequestMapping(value = "/foo", method = { RequestMethod.GET, RequestMethod.POST} )
	public String foo() {
		// ...
	}
}

A CorsConfigurationSource interface can be implemented by HTTP request
handlers that want to support CORS by providing a CorsConfiguration
that will be detected at AbstractHandlerMapping level. See for
example ResourceHttpRequestHandler that implements this interface.

Global CORS configuration should be supported through ControllerAdvice
(with type level @CrossOrigin annotated class or class implementing
CorsConfigurationSource), or with XML namespace and JavaConfig
configuration, but this is not implemented yet.

Issue: SPR-9278

Jackson 2.5.0 or later is required.

Issue: SPR-12501

This commit adds a filters property to MappingJacksonValue
and also manages a special FilterProvider class name model key in
order to be able to specify a customized FilterProvider for each
handler method execution, and thus provides a more dynamic
alternative to our existing JsonView support.

A filters property is also now available in Jackson2ObjectMapperBuilder
and Jackson2ObjectMapperFactoryBean in order to set easily a
global FilterProvider.

More details about @JsonFilter at
http://wiki.fasterxml.com/JacksonFeatureJsonFilter.

Issue: SPR-12586

* patch-1:
  Fix typo.

Issue: SPR-12501

Issue: SPR-12870

ReaderEditor supports Reader injection analogous to InputStreamEditor (from Spring resource location)

Also, EncodedResource implements InputStreamSource now since it declares getInputStream() anyway.

Issue: SPR-12876

Issue: SPR-12871

Prior to this commit, the `client-library-url` XML attribute was not
effective in the MVC namespace, leaving the default value configured:

```xml
<websocket:sockjs client-library-url="/js/sockjs.js" />
```

This commit fixes the sockjs namespace handler and makes sure that this
attribute is configured on the `SockJsService` Bean to be created.

Issue: SPR-12874

Netty4ClientHttpRequest ignores query params

Before this commit, Netty4ClientHttpRequest ignored query parameters
(?foo=bar). This commit fixes that.

Issue: SPR-12779

This commit introduces support for "Path Segment URI Variable
expansion", see https://tools.ietf.org/html/rfc6570#section-3.2.6.
In practice, this means that URI template variables prefixed with a '/'
are treated like path segments and - as such - will encode any '/'
found. For example: {/foo} expanded with "bar/baz" with result in
"bar%2F".

Issue: SPR-12750

AbstractContextLoaderInitializer and AbstractDispatcherServletInitializer support ApplicationContextInitializers now

Issue: SPR-12430

Issue: SPR-12870

Issue: SPR-11740

AnnotationUtils.getAnnotationAttributes makes Method accessible (analogous to AnnotationUtils.getValue)

Issue: SPR-12858

Issue: SPR-12863

BeanWrapperImpl.setPropertyValue throws InvalidPropertyException with correct property value for nested collection case

Issue: SPR-12866

Issue: SPR-12865

This change provides support for map[NEW], map[new], map[T]
and map[t]. Prior to this change the 'new' and 't' had to
be quoted because they were keywords in SpEL for a constructor
reference and type reference respectively.

Issue: SPR-11783

Issue: SPR-12855

- The exception message now mentions lacking to-Object method as well.

- Documented explicit lacking support for toString() for conversions.

- Introduced dedicated has*() methods for greater clarity and to reduce
  code duplication.

- Static factory methods (i.e., of, from, valueOf) are now supported for
  conversion to a String.

- Now correctly using @test(expected=...) where appropriate.

- Renamed DefaultConversionTests to DefaultConversionServiceTests.

- Moved all tests related to DefaultConversionService from
  GenericConversionServiceTests to DefaultConversionServiceTests.

- No longer printing to System.out.

- Removed all duplicate instantiation of conversion services.

- Now using Java 8 streams to simplify implementations of custom test
  converters. Also using streams in tests where appropriate.

The check for an empty request body InputStream is now in the base
class AbstractMessageConverterMethodArgumentResolver shared for
all arguments that involve reading with an HttpMessageConverter --
@RequestBody, @RequestPart, and HttpEntity.

When an empty body is detected any configured RequestBodyAdvice is
given a chance to select a default value or leave it as null.

Issue: SPR-12778, SPR-12860, SPR-12861

RequestBodyAdvice is analogous to ResponseBodyAdvice (added in 4.1)
but for intercepting for reading the request with an
HttpMessageConverter for resolving an @RequestBody or an HttpEntity
method argument.

Issue: SPR-12501

The rework of 314b069f in a7fec6a4 has created a lazy proxy to make sure
that the need for an exception cache resolver come as late as possible.

Unfortunately, the test that was only failing on CI because of an early
lookup has not been updated accordingly. This is now the case.

Issue: SPR-12850

This is a rework of 314b069f that may still lead to issue if a Cacheable
annotated bean is inspected on startup. Instead of resolving the default
exception CacheResolver if a cache operation is parsed, we resolve it as
late as possible (i.e. when an exception is thrown and the relevant
exception cache needs to be resolved)

Issue: SPR-12850

Issue: SPR-12814