dbcreator to process individual BED files by score/strand

[mdozmorov]

New categories of genomic features can be added to the main 'grsnp_db' database by simply creating folders and placing BED files there.

But we have score system. If BED files have 5th column (score), they can be filtered by score percentiles.

Can dbcreator have an option -f, --filter that takes a path to a folder, and filter each BED file there, placing the filtered ones into folders under grsnp_db_25, grsnp_db_25_plus etc.