* Store name of authenticated user in basicauth for use by upstream middleware such as fastcgi and cgi.
* Use request context to transfer name of authorized user from basicauth to upstream middleware. Test retrieval of name from context.
* Remove development code that was inadvertently left in place
* Use keys of type httpserver.CtxKey to access Context values
If a site owner protects a path with basicauth, no need
to use the Authorization header elsewhere upstream, especially since it
contains credentials.
If this breaks anyone, it means they're double-dipping. It's usually
good practice to clear out credentials as soon as they're not needed
anymore. (Note that we only clear credentials after they're used,
they stay for any other reason.)
