Retain and display /topic on top of log page

[sladen]

IRC /topic lines are regularly used for status information which falls into two categories:

1. Long-term; link to project Wiki/Github/Bug trackers
2. Short-term; outage status, people's birthdays, meet-up photo links

It would be useful for the user of the logs to be able to access both of this uses of /topic in an easy manner.

A possible solution catering to both requirements could be:

1. Display current /topic near top of near-time log
2. Display /topic changes/updates within the log at the time they happened