Need graceful shutdown for relays

On Windows, shutting down a To relay asks if you want to do a graceful shutdown, giving connected users time to find another relay. This should be possible in Linux too.

As it is, shutting down a Tor relay in Linux is an abrupt exit, anyone connected just has to wait for their connection to time out. On a busy node that is potentially thousand of people who know only that their web page partially loaded then hung.

I propose that a Close action be added to the existing Start and Stop (pardon my RedHat terminology) actions. This should delay a minute during which no new connections are accepted, then exit.

Trac:
Username: tmpname0901