Favorites servers fix, one server update and show privates.

Fixed favorites servers - they now correctly added/removed in/from cache,
and also fixed favorite server edition dialog, which now also takes
advantage from server's cache.

Added new toolbar button for updating one server. It works :).

Added new column in servers lists, which shows is server is private or public.

requester/requester_object.go

@@ -133,3 +133,7 @@ func (r *Requester) UpdateFavoriteServers() {
     r.pooler.UpdateServers("favorites")
 }
 
+func (r *Requester) UpdateOneServer(server_address string) {
+    fmt.Println("Updating server " + server_address)
+    r.pooler.UpdateOneServer(server_address)
+}