Alternative to servePlaceIds that uses GameId

[MrBlackbrow]

Hi! I'm a big fan of the servePlaceIds property in rojo's config. But I'm working in a big team and our project has dozens of places we need to serve to, and they change quite often.

So in this scenario, it would be a great quality of life improvement for us if the serving whitelist could be assigned on a per-experience basis using the GameId.