Default argument values contain hardcoded paths

[MarekGierlinski]

When running run_decoden without --blacklist_file specified, the script crashes with error:

FileNotFoundError: [Errno 2] No such file or directory: '../DecoDen_GV/data/annotations/hg19-blacklist.v2.bed'

This happens after a few minutes of calculations, indicating that the input arguments are not checked at the start of the code.