Add --format option to --list

[RhetTbull]

See discussion in #75. Add --format [json,csv,tsv] to --list that outputs the format in JSON, CSV, or TSV format. This allows user to create a report of metadata for one or more files.

Extend --include, --exclude (#76) to this new option as well.

JSON indentation could be specified thusly:

--format json:2 uses indent of 2
--format json:4 uses indent of 4, and so on
--format json uses 0 indent