Fix taxonomic similarity filter / column so that it uses the correct taxon rank

[lzy7071]

Currently, the column taxonomic similarity in Concentrations table seems to display the incorrect rank. When the organism is Escherichia coli, the taxonomic similarity column should display species, rather than genus that's currently shown.
The testapi for /metabolites/concentrations/similar_compounds/ or any other endpoints that need taxon calculations has been changed. The distances from the testapi can be directly used without any further changes with the list returned by /taxon/canon_rank_distance_by_name/, where the anchor organism's (E Coli. E1002) distance (1) is the index at which the taxon similarity can be found ({"Escherichia coli": 1, "rank": "species"}).