vault demo: multiple communities

[tgross]

@drew-512 wrote:

We def will have multiple communities out of the gate (to demo that as a powerful feature of PLAN), and this vault model works great to make that happen. Each feed, in PLAN, is a community URI is a sequence of txns as you are well aware. So as we demo, say, 5 communities, maybe 3 will be on one and 2 on another. Either way, a system where a pnode can ultimately start getting a txn feed for a given community URI on the fly, then we're golden and we will clean up in 2021 as we start to demo.