FTP: Add anonymous setup, add utf-8 setup, add error message handling information, add "not too many rights" information

[DarkTrick]

I suggest to add the following information to the server guide:

[1] regarding error messages from the server:
- Are not given. Error messages are only sent to clients. However, clients like Nautilus will not show error messages. For troubleshooting a tool like FileZilla is suggested.

[2] regarding anonymous access:
- To enable full anonymous access its necessary to set
  1) Enable read/write/execcute access on file system level (chmod)
  2) Enable the options you need (within /etc/vsftpd.conf):

    # make dirs: drwxrwxrwx and files: -rw-rw-rw-
    anon_umask=0000
    #anon_umask is only for newly created files
    # (rightclick → create file). It is not for copied files.

    anonymous_enable=YES

    # If the following is NO file and dirs can be created, but not renamed or deleted
    anon_other_write_enable=YES

    anon_upload_enable=YES
    anon_other_write_enable=YES
    anon_mkdir_write_enable=YES

[3] regarding too many rights:
- The ftp root directory must not be writable by anyone (owner/group/others). Otherwise the ftp server will not work (It will start without an error message though; be careful) --> This might only be a problem, if anonymous access is allowed; I didn't check.

[4] regarding UTF-8:
- Enable UTF-8 for filesystem:
    add "utf8" in the options column within /etc/fstab
- Enable UTF-8 for server (within /etc/vsftpd.conf):
    utf8_filesystem=YES
- FYI: Enable UTF-8 in client:
    Default bash in ubuntu (not "terminal") does not support UTF-8 filenames. You server could work properly, even if filenames are not shown properly inside the terminal.

[5] regarding using external storage device:
- Example mounting for external storage:
  /dev/sda1 /ftpHome/files vfat rw,exec,utf8,umask=000 0 0
     - rw: says, that storage will be read-/writable. This is the storage/mount level. If it's "readonly" here, it doesn't matter what the ftp server conf says
     - utf8 enables UTF-8 on storage/mount level
     - umask=000 set full access to all files on filesystem level. Be aware, that this is a *u*mask, not a mask. So it works invers to the numbering used in chmod.

[6] regarding ftp root directory for anonymous access:
- vsftpd daemon uses a user (default: ftp). The home direcory of this use will be the ftp root directory for anonymous.