add info about rclone on transferring files b/ midway and clouds

[aolykhin]

https://rt.rcc.uchicago.edu/rt/Ticket/Display.html?id=52373

[pcarbo]

@aolykhin I don't know if we should be officially advertising rclone; previous Systems Team people had concerns about widespread use.

[jdlaurence]

Yes, I think globus, samba, and scp are our officially supported data transfer mechanisms. I'll close this for now