Show XEP-0203 timestamp if given.

If a message was delayed and includes an XEP-0203 timestamp of the send
time, show that rather than the receive time.

Thanks to Peter Stuge.
Add chat, xa, dnd, online and away commands.

Thanks to Peter Stuge.
Update terminal size on change.

In order to work property, this change needs ssh/terminal to be updated
to include https://codereview.appspot.com/105580043.

(Although it doesn't always work great with gnome-terminal and I'm not
sure that it ever can.)
Copy Pond's recognition of a Persistent folder on Tails.