`as.mo()`: give preference to species if subspecies is non-existent

[msberends]

Now, this happens:

as.mo("Neisseria mucosa sicca")
#> ℹ Microorganism translation was uncertain for "Neisseria mucosa sicca" (assumed Neisseria elongata glycolytica).
#>   Run mo_uncertainties() to review this, or use add_custom_microorganisms() to add custom entries.
#> Class 'mo'
#> [1] B_NESSR_ELNG_GLYC

Instead, you'd expect this:

as.mo("Neisseria mucosa sicca")
#> ℹ Microorganism translation was uncertain for "Neisseria mucosa sicca" (assumed Neisseria mucosa).
#>   Run mo_uncertainties() to review this, or use add_custom_microorganisms() to add custom entries.
#> Class 'mo'
#> [1] B_NESSR_MUCS

Thus, if a subspecies is not in our microorganisms table, prefer the species over some exotic try to find something.