Changed architecture for processing blast assignments to decrease memory usage
Adjusted resource request for cross-donor
1. fixed header line to only write to tophit file once
2. 1.3 now uses split v-blast files (instead of vgerm_tophit) for memory efficiency
3. fixed bug in calculation of frame for negative strand reads
4. added informative error message to generate_blast_tophits utility routine in case of empty blast results file