tunneling and exec channel request support for SSH URIs

[Jim Wigginton <wiggie%alumni.cs.utexas.edu@localhost>]

I was thinking about SSH URI's some and I think it'd be neat if the
draft for SSH URI's supported tunneling and exec style channel
requests.  eg.

ssh://user%host.example.com@localhost/exec:ls%20-la

...or...

ssh://user%host.example.com@localhost/tunnel:www.google.com:80

As is, the only thing that SSH URI's, as defined in the draft
(draft-ietf-secsh-scp-sftp-ssh-uri-04), really support, it seems, are
retrieving files via SFTP and opening interactive shells.  And
although that, I suppose, has its uses, I think SSH URI's could be
made a lot more versatile by adding support for the above.