Optimize the IgBLAST step to process target sequence data

[nsyzrantsev]

IgBLAST step should process FASTQ1, FASTQ2 and FASTQ12 in three separate jobs: process IgBlastFASTQ1 {...}, process IgBlastFASTQ2 {...}, process IgBlastFASTQ12 {...}. Each job should have label "process_low".

This improvement allows to process target seq data faster, if user have enough resources for it. Otherwise IgBLAST will work as before.