211 - format downloaded bundle's name based on dataset type; add `.tar` suffix

Created by: ri-pandey

Description

1. Changes the name of the bundle that is generated and downloaded according to {dataset_name}.{dataset_type}.tar.
2. Adds a script to unstage all datasets that are currently staged.

Related Issue(s)

Closes #211 (closed)

Changes Made

List the main changes made in this PR. Be as specific as possible.

• Feature added
• Bug fixed
• Code refactored
• Tests changed
• Documentation updated
• Other changes: [describe]

Checklist

Before submitting this PR, please make sure that:

• Your code passes linting and coding style checks.
• Documentation has been updated to reflect the changes.
• You have reviewed your own code and resolved any merge conflicts.
• You have requested a review from at least one team member.
• Any relevant issue(s) have been linked to this PR.

Additional Information

1. This approach ditches the bundle alias, which has been used until this point to determine the name of the downloaded bundle. Instead, bundles to be downloaded are now generated by the pattern {dataset.name}.{dataset.type}.tar.
2. This change does not need to update the names of the tars that are already archived to SDA.
3. An existing dataset (one already registered in the system) will need to be unstaged, and then staged again for the bundle to be downloaded with the new name. If the existing datasets are not unstaged and then restaged again, the download of those datasets will fail. There is a script added that achieves this - unstage_datasets.js
4. New datasets archived henceforth will be archived with the updated name pattern {dataset.name}.{dataset.type}.tar.