Re-written, to include these features
(a) Faster dumping (aobut 25% of the tome compared with before)
(b) Non-redundant dumping - 2-way xrefs are only populated one way (faster loading)
(c) For t3 species, we only create an Ortholog_other (and Protein/Peptide)
   the canonical transcripts, rather than all transcripts of the orthologous
   gene