chatroom 6.x-2.0-alpha2

this is a big update. many, many bugs fixed from 6.x-2.0-alpha1, and some nice new features.

this branch now has more features than the 6.x-1.0 branch, and although its a long way from stable, is now a lot less likely to kill your kittens.

this is ready for wider testing, but not yet for production use, and there no upgrade path from the 6.x-1.0 branch yet.

• make the user online list actually update properly
• preliminary user picture support with imagecache integration for chat online lists
• add default teaser theming for chat and chatroom nodes, giving useful info in list view
• many caching fixes, so this is now much easier on the server than the 6.x-1.0 branch
• new message alerts, only via the browser title bar, but sound is on the todo list
• many, many bugfixes for the new node-based chats
• much old crufty code thrown away, slowly making headway to maintainability