Consider FTP-based access of IDR data

[d33bs]

I noticed this project leverages Aspera to help download IDR data. In searching through documentation and image.sc forum posts, I came across this IDR download instructions page, which indicates you can now use anonymous FTP access for downloading IDR data. It might be helpful to move over to this approach, especially as there are built-in FTP clients within Python. The advantage of reducing code-complexity here might need to be balanced with Aspera's download performance considerations (if it's faster than FTP).

May relate / overlap with efforts in #4 (S3-based access of IDR resources).

For example:

from ftplib import FTP

# Connect to the FTP server
with FTP("ftp.ebi.ac.uk") as ftp:
    # Log in to the FTP server
    ftp.login(user="anonymous", passwd="")

    # Change to the desired directory (optional)
    ftp.cwd("/pub/databases/IDR")

    # List directories
    dirs = []
    ftp.dir(dirs.append)

    # Print the list of directories
    print("Directories on FTP server:")
    for dir_info in dirs:
        print(dir_info)