Automated tagging of grid jobs

For reproducibility, a nice feature to have is to create a tag every time a significant production of training is run. This adds a CLI for submit-single-btag with the following args:

 -h: get help
 -c  path to config file to use
 -t  tag the current commit using the supplied string
 -d: perform a dry run (no submit)
 -f: force submit even if uncommited changes exist

A few convenience options, like overwriting the default config with -c or adding a readable description to the job out name with -d are provided. If the user specifies that they want the job to be tagged with -t, the script looks for a tag associated with HEAD. If one isn't found, a tag is created using the current date and the most recent commit hash. By default, the script does not allow the user to run -t if uncommitted changes exist in ./training-dataset-dumper.

Things to improve:

• It would be nice to standardise this functionality to the other submit scripts too. I know @dguest has mentioned creating a wrapper job submission script, so we could move the CLI and tagging functionality there when that is done.