Airflow tasks to fetch GWAS Catalog curated datasets

[DSuveges]

Currently the GWAS Catalog datasets are updated via a shell script under /utils. However this is not the preferred way. Instead, files needs to be updated via the same Airflow DAG that prepares the new curation table.

Expectation from the update:

• [ ] Get the same set of metadata as the shell script.
• [ ] Get release version.
• [ ] Write log to the manifest folder.
• [ ] Fetch files then upon success, overwrite old files in bucket.