Add CLI support for identifying files in a commit range of a VCS

[alilleybrinker]

One important operation for OmniBOR will be to produce Artifact IDs for vulnerable files between some commit range in a VCS. It would be great if the CLI supported it. This could be something like:

$ omnibor artifact vuln --start <COMMIT_HASH> --end <COMMIT_HASH> [<FILENAME>...]