Add user interface element for taxonomic search filtering

[yannickwurm]

THis has come up several times.

In the online BLAST from NCBI, there is the ability to exclude synthetics, uncultured organisms, or a specific species. Is there a similar option within the sequence server 'BLAST'

Every "species" has a taxid - as does this:
e.g.: https://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?id=81077

Similarly to NCBI, we want a UI element that allows users to type species names to be excluded. That would lead to, for example the ofllowing being added to params.

-negative_taxids 81077

Several can be comma-delimited (and we wnat to be able to support this).

[yannickwurm]

this is for filtering of database sequences (not of query sequences).

it likely wants to rest on the ncbi taxdb that is downloaded alongside some databases via the update-blastdb.pl script (or a JSON equivalent)