[ftputil] server_format / custom directory format parsing

[Terrence Brannon]

Per http://www.sschwarzer.net/python/ftputil.html#set-directory-format

I am wondering if the support for custom directory parsers is in
place. I am tackling the Connect:Enterprise UNIX FTP listing format:

ftp> dir
227 Entering Passive Mode (199,125,13,20,188,78)
150 Opening ASCII mode data connection for .
-CR--M----FTP B kNLeX8       5286      231 Jan 31 08:12 compile-myself
Total number of batches listed: 1
226 Transfer complete.
ftp>