core: adding 'radosgw-admin' command support

[subhamkrai]

adding support for 'radosgw-admin' command in the cli tool and also adding docs and ci.

Issue resolved by this Pull Request: Resolves #253

Checklist:

• [ ] Commit Message Formatting: Commit titles and messages follow guidelines in the developer guide.
• [ ] Reviewed the developer guide on Submitting a Pull Request
• [ ] Documentation has been updated, if necessary.
• [ ] Unit tests have been added, if necessary.
• [ ] Integration tests have been added, if necessary.