Consider running a textile gateway alongside in `threadsd`

[carsonfarmer]

This came up during a discussion with @andrewxhill. What if every threadsd also side-car'd (or however we decided to implement it) a textile gateway that was capable of rendering bucket-style content. In the case of threadsd, this would simply render whatever arbitrary JSON-like data was available under a given thread/instance. This is slightly more nuance because we're talking about arbitrary data structures at the thread level, but worth a discussion. As it would make it possible for devs interested in running their own services to also provide a gateway to support their users etc directly. Couple this with #316, and we've have most of what we'd need for a large swatch of use cases.