Currently pegasus-transfer cannot handle ftp to file transfers.
This was mainly left out due to the difficulty of handling the ftp credentials.

However there are ftp servers that don't require authentication like noao (example: ftp://archive1.dm.noao.edu/ToO/ToO-raw/20190510/2019A-0205/ ) and we should be able to support these.

Task description: Add support for FTP to File transfers in pegasus-transfer from ftp servers that don't require authentication.