Revert inadvertent change to DefaultDocumentLoader

Revert changes to DefaultDocumentLoader accidentally committed in
60532cbd1eb4e1b5778653fec315407531e949a9.
Add ConversionService support for ByteBuffers

Add ByteBufferConverter that is registered by default with the
DefaultConversionService. Allows conversion from/to a ByteBuffer and
byte[] or to any type that can be converted via a byte[].

Issue: SPR-10712
ConversionService JSR-356 Encoder/Decoder adapters

Develop support class allowing JSR-356 Encoder and Decoder interfaces
to delegate to Spring's ConversionService.

Issue: SPR-10694
Merge branch 'SPR-10694'

* SPR-10694:
  ConversionService JSR-356 Encoder/Decoder adapters
  Add ConversionService support for ByteBuffers
Upgrade spring-websocket to Jetty 9.0.4
Fix typos in HandlerAdapter
Fix typo in ModelAndViewMethodReturnValueHandler

This commit fixes a typo in the class-level Javadoc for
ModelAndViewMethodReturnValueHandler.

Issue: SPR-10650
Merge pull request #314 from bijukunjummen/master

* SPR-10650:
  Fix typo in ModelAndViewMethodReturnValueHandler
Merge remote-tracking branch 'origin/master'
Request streaming for Apache HttpClient

- Added org.springframework.http.StreamingHttpOutputMessage, which
  allows for a settable request body (as opposed to an output stream).

- Added http.client.HttpComponentsStreamingClientHttpRequest, which
  implements the above mentioned interface, mapping setBody() to a
  setEntity() call on the Apache HttpClient HttpEntityEnclosingRequest.

- Added a 'bufferRequestBody' property to the
  HttpComponentsClientHttpRequestFactory. When this property is set to
  false (default is true), we return a
  HttpComponentsStreamingClientHttpRequest instead of a (request
  buffering) HttpComponentsClientHttpRequest.

Issue: SPR-10728