Merge pull request #6214 from RosettaCommons/roccomoretti/interactive_server_alert
[Foldit] Add warning when you're logging in to alternate server.
Add a line to the Play Online dialog which warns when you're logging into a site which is not the OPTION_SERVER_URL_DEFAULT.
There should be no change in the display when you're using the regular login site.
(Internal only change: No Release Notes)