[http-server] Move connection keep-alive handling.

This moves the code from the server's response handling
code to the response's initialize method.
[http-server] Simplify response initialize method.

Remove the direction: keyword argument and validation as it isn't
needed.
[http-server] Just create <request> rather than make it configurable.
[http-server] Collapse some whitespace.
[dsp] Fix serious warning due to "<dylan-server-page".
Merge pull request #75 from dylan-lang/cleanups

Cleanups
Fix bit-rot in http-protocol-test-suite.
Merge pull request #76 from cgay/client

Fix bit-rot in http-protocol-test-suite.
Update URL in http-server-demo README file.
Use <byte-string>s for request methods and http version specifiers.
[server] Use <http-method> to represent request methods.
checkpoint