Add reduce_2field reduce option
Batch csv pyard-reduce-csv takes in reduce_2field option to reduce 2 fields alleles like B*15:220, DPB1*104:01 and A*02:642
Batch csv pyard-reduce-csv takes in reduce_2field option to reduce 2 fields alleles like B*15:220, DPB1*104:01 and A*02:642