1. Support for PUT.

The big change is support for uploading via the master server, based heavily
on the prototype that Grant did. Currently only host-based (IP-based)
authentication is done as is the case with download. Grant's SSL-based
authentication code is "integrated" but has not even been compiled in.

The PUT protocol allows for assorted gewgaws, like specifying a maximum size,
setting a timeout value, returning size and signature info, etc.

There is a new, awkwardly-named client utility "frisupload" which, like the
download client, takes an "image ID" as an argument and requests to upload
(PUT) that image via the master server. As with download, the image ID can
be either of the form "<pid>/<emulab-image-name>", to upload/update an actual
Emulab image or it can start with a "/" in which case it is considered to
be a pathname on the server.

On the server side, the master server takes PUT requests, verifies permission
to upload the ima...