Default sample material dropdown has no way to add a missing value

[jeandavidt]

Problem

The Default sample material dropdown on the Person form only offers a fixed vocabulary (grit, domestic wastewater, combined wastewater, stormwater, preliminary/primary/secondary effluent, ...). If the material a person actually samples isn't on the list, there's no way to create it from this form.

Expected: Allow creating a new sample material value on the fly (or link out to the vocabulary admin page) when the needed value doesn't exist yet.