Some UI changes

Heya,

I took the liberty to change how the schedule items are shown, so it's easier to create a schedule that shows the actual time used.

I've also added a couple of new CSS classes, for 10minute, 20min, &c. time slots. I suggest that we use those instead, since it's *very* useful to know exactly how much time is used for *everything* (including the 10-minute breaks between 20-min topics!)

Didn't update the json file with this though. :)

- Salve (sjn, Oslo.pm)