add server-info pages to WUI, link there from upload/download status pages and Welcome page

[warner]

I was looking at one of the status/mapupdate pages today (the "Recent Uploads and Downloads" pages), and it occurred to me that it'd be great if the "Per-Server Response Times" pages could link to a page that describes what we know about that server.

The Welcome page also has a line per server, and it could link to the same place. That would give us a page to describe things like:

• server-id, TubID, nickname
• how we learned about it (introducer, local override)
• (maybe) how we connect to it (FURL connection hints) (but might be sensitive, if a Tor hint was overridden locally)
• connection history
• accept/did-not-accept share history, had/did-not-have share history
• latency/bandwidth history

And in the future, this will be a place to show Accounting information, storage provided/consumed quota data, and maybe control knobs to enable/disable storage service. Also it would be a fun place to put a "send a message to the server operator" text box.