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

[martindholmes]

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.

[martindholmes]

As of commit 7a4c4c0, all remaining issues on the current set of diagnostics are fixed.

[martindholmes]

Added some stats today.