GTDB and RefSeq-RDP databases parsed for species assignment

GTDB and RefSeq-RDP databases parsed for the addSpecies() dada2 function. Both databases were parsed with `parsing_DB_dada2_spp_assign.py` python script using as input both databases downloaded at: https://zenodo.org/record/2541239#.XM2UgCOZPOQ. The python script and a detailed description explaining the code and databases versions can be found at: https://github.com/antonioggsousa/GTDB-RefSeq-RDP-assign-spp-dada2