Use a JSON file instead of UDP Versionsrv

Could also be a part of https://github.com/TeeworldsArchive/website

Make the client just get the https://archive.teeworlds.wiki/version.json

e.g.
```json
{
    "maps":
    {
        "name": "map name",
        "size": 20260325,
        "crc": 20260327,
        "sha256": "replace this with sha256 string",
        "version": "0.7.1-0.7.3"
    },
    "version": "0.7.6"
}
```