Add FTP support

[Endaris]

Using luasocket: https://lunarmodules.github.io/luasocket/ftp.html#get

This would either

• need changes to the layout of releaseStreams.json to communicate the protocol type to use in an easy to parse manner; this would be a breaking change
  or
• require some (more involved) logic for parsing the protocol from the url

Needs a new "type" for the server endpoint to enable a different processing for nlst returns from ftp as the parsing will work differently than from the nginx directory representation.