Add 'ftp' as a copy method

copy_method="ftp"
-m ftp

The 'ftp' copy method is almost identical to the 'sftp' method. The difference is that the home directory will be stripped from the filename, under the assumption that the FTP server is chrooting connections. So a relative path for the filename is used, if the first part of the path matches $HOME. You can disable the relative path behaviour by setting ftp_absolute=1 in your ~/.rbbedit file.