fetch_all_by_biotype  added

Change in UNIQUE index on xref results in many more GO terms (apparently) being projected, but this is because the same GO term projected from multiple sources now gets multiple rows in the xref table, whereas before, because info_type/info_text wasn't being considered, only one row would have been created.

length as the original exon, returning undef if not (can happen when
only part of the exon could be transformed)

committing intermediate state of module before rewriting it to use lightweight feature object for caching

feature itself does not transform cleanly and the co-ordinates of the
transformed gene are inferred from the transformed transcripts/exons.

FlyBase genes which have names