UTF-8 support and being Google Chrome-friendly

Hi,

I've made some changes to Bifrost to accommodate UTF8 support (as per RFC 2640), and also to increase support for Google Chrome as FTP client. In the latter case, the problem was in that Bifrost translates {error, _} from Mod:change_directory() to 450 error code, and Chrome tries to CWD into each entity to determine if it is a file or a directory. 450 error seems to confuse it, while 550 is treated as "action unavailable", as per RFC 959 (so Chrome decides the entity is a file).

Hope you'll find them useful.