Add users being away

Via a toggle in the mwchat-me section.
An away user will have a lighter background color, greyer text, a tooltip,
and on some browsers, a greyscale avatar
Requires update.php due to field addition in chat_users table
Bump version
Change online users format

Change-Id: I99675f26f00c517784b021ca69e0edd24496ba7d