Make Epi Trackers stratified on identification status

[AdrienLeGuillou]

It could be interesting to look at the outcomes on 2 sub-populations:

• those never identified
• those who were identified at some point

I need to find a way to make them relevant

[smjenness]

@AdrienLeGuillou : closing this because this is stale at this point. Let me know if you think otherwise.