Template parsing failing due to missing REMARK 410 section

[DarioMarzella]

Some structures when downloaded (e.g. 7MJA) miss the REMRK 410 section from IMGT.
This causes some steps like allele assignment or secondary structure assignment crash while generating the database.

A solution can be to split construct_both_blast_db() (from branch mhcii_DM) in two, generate the refseq_blast_db before parsing the pdbs and use it to assign the allele names.