Prepopulation of data including room topics.

[ldang]

It would be more fun for the editors and reviewers if they knew what topic each room stream is covering, before they chose it to edit.

If there is info in the signs.xml and what track the first talk in each room stream belongs to, perhaps we could prepopulate the Info field, to label the room.

We still want to use the Info field for freeform text, as it's useful to mark any issues with the stream