Diagnostics: reminder to check, fix, and add new ones

The diagnostics page is on the site here:

https://hcmc.uvic.ca/project/bbti/diagnostics.html

and anything showing up as red will need fixing. This ticket is also to solicit any suggestions for new diagnostics; if you find some kind of error in the data, and you think it might be systemic or common, we can add a diagnostic test to catch cases of it, so they won't be missed.