App::PgCryobit::Shipper::FTPShipper - A Shipper to ship the backup files via FTP.
ftp_host - The address of the FTP server to connect to
ftp_user - The user to connect as
ftp_password - The password to use on connection.
backup_dir - The directory inside the ftp server where to manage the files shipping. MUST exist.
Returns a fresh connection to the ftp server.