Add support for changing job_jobid_status.tsv filename

[mawilson1234]

It would be helpful to be able to change the name of the job_jobid_status.tsv file. (In particular, I would find it useful to be able to allow it to use the job name.) Currently, it's only possible to change the directory the file is saved in using --status-dir, or to suppress the file entirely using --suppress-stats-file. I've added code to dSQBatch.py that should allow the user to specify the name of the stats file using a command line argument --stats-file. The default value is the same as the current hard-coded filename, job_jobid_status.tsv, so this should be backward compatible. In addition, %j can be used to specify the job id when specifying this argument, as it does in SBATCH options. I've also updated README.md to reflect this change.