organizational shuffle - use package SwiftViz as the collection point for visualization tools

[heckj]

When I started this repo, I was aiming to clone/port concepts from D3 directly over to be useful as native constructs in Swift.

Most of what's in SwiftViz today is the Scale concept, and I've created a separate repository for Chart. I suspect the best future use of this package is as a holder to a collection of the separate packages - a swift visualization toolset. But... I want to use what's in this repository as a dependency on Chart, so it's somewhat backward.

As such, I'm going to refactor and pull the Scale pieces into their own (new) repository under this org: Scale, and then import that here to expose it as well.

(I think this will also make it easier to have a more limited/clean API for those wanting to use something like Chart - as well as handle the dependency mapping per platform where some elements might not be available)