Ref T11816.
- Now that we can do something meaningful with them, bring back the yellow dots for "busy".
- Default to "busy" when attending events (we could make this "busy" for short events and "away" for long events or something).
- Let users pick how to display their attending status on the event page.
- Also show which event the user is attending since I had to mess with the cache code anyway. We can get rid of this again if it doesn't feel good.
