Fixing shipments import

This Pull Request fixes multiple issues with the Trade Data import:

- Was not importing trade on 'N' status taxa (TODO: make sure that users can search by taxa with 'N' status)
- Issues with the mapping of cites_taxon_codes against species plus ids
- Issues with fake synonyms. These have now been changed to be Trade names.

TODO: Once all is good we should tidy up and remove these large import tables, and their large indices.