[Done] Proposed Repositories Organization

@Pertti We are not planning tons of side projects, but we hope to make it easy for the community to do so.
When we started planning CI4, one of the things that was clear was that the community liked the idea of a download-and-run single project, without having to pull in a bazillion other subprojects. In other words, stick to the core.
That is part of what this repo reorganization is about - purpose-building the essentials, downloadable or composer-installable