Replace "exact separated text fragment(s)" with "exact text fragment(s) separated by semicolons"

[fedarko]

This will let us deal with taxonomy strings that include spaces (e.g. k__Bacteria; p__Proteobacteria; c__Gammaproteobacteria; o__Oceanospirillales; f__Halomonadaceae; g__Candidatus Portiera; s__), because those apparently exist. Huh.

This will also make things clearer for users IMO (taking care of this would be sufficient for #123, I think).