JIRA: https://jira.spring.io/browse/INT-3737
Support returning an `InputStream` from a GET operation.
This can be used in conjuction with a `<file:splitter/>` to stream a text file.
The user is responsible for releasing the session when the download is complete.
The session object is stored in the message header and `RemoteFileUtils.closeSession()` should be called
to clean up and close the session.
INT-3737: Polishing and Docs
Fix `CachedSession.close()` bug
Preventing `Caused by: java.io.IOException: Previous raw read was not finalized`
when `Session` is returned to the pool, but `readingRaw` hasn't been finalized
because the real `close()` isn't invoked in case of normal return to pool.
65d2024937