Issue: SPR-13776

Issue: SPR-12196

Added extension to Future with capabilities for registering callbacks
when the future is complete.

- Added ListenableFuture, ListenableFutureCallback,
  ListenableFutureCallbackRegistry, and ListenableFutureTask.
- Using ListenableFuture in AsyncRestOperations/AsyncRestTemplate.
- Added AsyncListenableTaskExecutor, implemented in
  SimpleAsyncTaskExecutor.
- Added FutureAdapter and ListenableFutureAdapter.

Added AsyncRestTemplate, the asynchronous counterpart to the
RestTemplate that was introduced in Spring 3. All methods on the
AsyncRestTemplate are similar to those found on the synchronous
RestTemplatem, except that they return Future wrappers instead of
concrete results.

To enable this, this commit introduces the AsyncClientHttpRequest and
AsyncClientHttpRequestFactory, similar to the ClientHttpRequest and
ClientHttpRequestFactory, except that ClientHttpRequest returns a
Future<ClientHttpResponse> for the execute method. Two implementations
of these interfaces are provided, one based on the HttpURLConnection
incombination with a Spring AsyncTaskExecutor and one based on Apache
HttpComponents HttpAsyncClient.

Issue: SPR-8804

Issue: SPR-10130

Add setOutputStreaming on SimpleClientHttpRequestFactory to allow the
disabling of 'output streaming' mode on the underlying connection so
that authentication and redirection can be handled automatically.

Issue: SPR-9617

Prior to this commit several HTTP classes made use of FileCopyUtils
when reading from or writing to streams. This has the unfortunate
side effect of closing streams that should really be left open.

The problem is particularly noticeable when dealing with a
FormHttpMessageConverter that is writing a multi-part response.

Relevant HTTP classes have now been refactored to make use of a new
StreamUtils class that works in a similar way FileCopyUtils but does
not close streams.

The NonClosingOutputStream class from SimpleStreamingClientHttpRequest
has also been refactored to a StreamUtils method.

Issue: SPR-10095

This reverts commit 45fa5082, reversing
changes made to a312d900.

Issue: SPR-10130

Issue: SPR-10127

Ensure that NonClosingOutputStream calls with a byte array call the
corresponding methods of the underlying OutputStream rather than
relying on the default NonClosingOutputStream implementation, which
writes one bte at a time. This significantly improves performance.

Issues: SPR-9530

This renaming more intuitively expresses the relationship between
subprojects and the JAR artifacts they produce.

Tracking history across these renames is possible, but it requires
use of the --follow flag to `git log`, for example

    $ git log spring-aop/src/main/java/org/springframework/aop/Advisor.java

will show history up until the renaming event, where

    $ git log --follow spring-aop/src/main/java/org/springframework/aop/Advisor.java

will show history for all changes to the file, before and after the
renaming.

See http://chrisbeams.com/git-diff-across-renamed-directories

refactored HTTP support into top-level package "org.springframework.http"; revised RestTemplate facility in package "org.springframework.web.client"