Delete files and corresponding index when they are removed from the filenode

[garvk]

When a file is removed from the FileFields Node then the file should also be deleted from the storage. Also, It's 'index' if created should also be deleted.

For example, if second file is removed in the screenshot, its file and index should be deleted.

Likely steps:

1. Create two endpoints in flask_app.py to delete file and delete index with necessary inputs
2. Call the two endpoints when file is removed