Implement public files in DNS response

[PedroHLC]

Here's how I got it working on ehelix:

%{
  type: "npc_download_center",
  meta: %{
    password: "",
    nip: ["network", "ip"],
    public: [ %{
        id: "somefile",
        name: "ILikeIceCream",
        extension: "exe",
        type: "cracker",
        modules: [ %{
          module: "overflow",
          version: 4
        }]
      } ]
  },
  content: %{
    title: "example"
  }
}

[renatomassaro]

Fixed on #301. I've changed the module key to name, so something like:

modules: [
  %{
    name: "overflow",
    version: 24
  }
]

Pas.