Support transcript switching

[SteveMarshall]

Whilst, longer-term, we need to support multiple transcripts elegantly in the UI (per #110), we should start with simple transcript switching.

This will require some amount of work on search, as well as a little design for transcript switching and, finally, updates to the frontend.

[hannahdonovan]

Hey Steve, James has got me up to speed on this. I think we just need to find some time to sit down together and prototype how the interactions work. Some night this week or next?

[SteveMarshall]

@hannahdonovan: Sure; I can do every night but Monday/Thursday this week, and every night but Friday next week.

[jaylett]

Or possibly just jump to #110 now…

[jaylett]

I have a simple draft for jumping into different transcripts from the mission homepage, by phase. A similar approach could be used on the phases page as well. (This is on top of in-transcript switching, once we figure out how that should look.)