Updated the dockerfile to use a two stage process. Snakemake image is used as the runtime environment.
Supports / Partially addresses #17

Updated snakemake workflow to work with Dockerfile. Also fixes module not found error by exposing pythonpath. Partially addresses #17

Partially addresses #28 and #17
User can now provide range (e.g. --workflow-ids 1-40) or omit this to download all workflows

- Temporary fix for ValueError with multiple context URLs (#34) by returning empty context for URLs that don't match allowed_urls_pattern.

FromAsCasing - FROM and AS should be in the same case.

- Added get_max_id_from_files method.
- If --workflow-ids argument is not provided, created_files.json should contain all workflows downloaded. get_max_id_from_files() finds the maximum ID in the sourced workflows.
- Part of wider effort to address #17

Removes list_expected_files() method.

- Added progress bar and removed line-by-line logging for easier evaluation of download and processing progress.
- Addresses #33

- Added preliminary module create_ro_crate to create an RO crate for a given file.
- Addresses #37

- Added a rule in Snakemake workflow to create an RO crate.
- Addresses #37

Addresses #37