Add tbl2asn branch to Darth pipeline

[taltman]

In order to automate a bulk submission to NCBI, we need to use tbl2asn:

https://www.ncbi.nlm.nih.gov/books/NBK53709/#gbankquickstart.when_is_tbl2asn_a_good_a

https://www.ncbi.nlm.nih.gov/genbank/tbl2asn2/

We'll add a step to the Darth annotation pipeline to auto-create the ASN.1 file, ready for submission to NCBI.