MLST/MLSD, bugfixes to LIST, legacy character encoding support

Hi! I have made some changes to the goftp package and thought you might be interested in merging them into your repository:
- MLST/MLSD command support
- LIST: fixed date calculation bug (if we are in January, December means December of last year, not of current year), timezone conversion
- If TranslateEncoding flag is set and server does not support UTF8 (according to FEAT response) , ISO-8859-15 is assumed and file name encoding is automatically adjusted in file/directory commands.