Add options for highlighting/filtering schedule (and talks list) by track

[drnlm]

It seems like a good idea to allow attendees to quickly see which talks are part of a given track, rather than having to go to individual talk pages.

For the schedule, since we include the track in the table cell properties, providing some way of selecting a style that highlights the given track is probably a good enough first solution.

For the talks list, maybe providing sub-pages that are track specific?