Rename client status to data, add group data.

We now distinguish between status, which is maintained by the server,
and data, which is provided by the client.  In addition to client data,
we now support group data.

webserver/webserver.go

@@ -339,7 +339,7 @@ func groupStatusHandler(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
-	d := group.GetStatus(g, false)
+	d := g.Status(false)
 	w.Header().Set("content-type", "application/json")
 	w.Header().Set("cache-control", "no-cache")