Create an API endpoint to download data from NCBI - through Download tool of Candis.

[rupav]

This will be used to download data from NCBI into Candis.

Checklist: to implement

• Add API endpoint to call Entrez module.
• Add GEO module
• Implement Esearch
• Implement Esummary
• Implement the logic as described in https://www.ncbi.nlm.nih.gov/geo/info/geo_paccess.html#ExampleIII
• Use socket.io for download progress.
• Add test cases
• Remove time.sleep()
• Setup logging instead of print statements. - refer Add a common logger module for logging in different modules. #137
• Start redis server from Procfile (now using honho Manager class) - use different port if initialized. - refer Start Redis Server using honcho Manager class. #99
• ftplib is used for downloading- show progress bar (It shows up with 'wget')
• Integrate with front-end. - refer issue Integrate frontend entrez form with backend #110 TODO: Improvements needed as mentioned in the related PRs to Integrate frontend entrez form with backend #110
• Add JS test cases for the same.
• Instead of using requests.Timeout error, use custom error class.