Add gene feature to genbank file without version

With this change the genbank parser no longer discards incomplete genes directly but keeps them as long as they have complete features annotated.

For example, the PIK3R2 gene is annotated on NC_000019.9 (or a slice) as 4973..>22328 with two RNA entries. One of these, however, is complete so it would be a shame to discard the entire gene.