Pr cmake

[dirkcgrunwald]

1. Add build multi-platform build support using cmake
2. perform builds using github actions
3. Fix minor Windows / C++ incompatibilities (intermixing wchar/char output)

[JayKickliter]

I cloned this PR and did my normal CMake based build steps and it built just fine. I didn't have to read any build instructions and there weren't any surprises. Built on macOS+M1.

[JayKickliter]

I've created rust wrapper for this branch and we're using it in production at decent scale. I'd love to see this work merged, otherwise there's a decent chance of having long-lived forks people depend on.

[wkozmaNTIA]

We're going through some internal reorganization with the larger PropLib effort over this winter, which will include work being done in this branch. Sorry its taken longer than it probably should. Just how things are being prioritized.

[dirkcgrunwald]

I'm happy to help however I can. Good to know the patch has been useful.

@JayKickliter - I'd be interested in learning about the project you're doing. Looking at the HexTree and geoprop repos, it looks like you're developing something that I had been hoping to work on within NSF SpectrumX similar to what e.g. https://cloudrf.com/ does but in a way that can support open datasets and new prop models.

Email is grunwald@colorado.edu

[JayKickliter]

@dirkcgrunwald you nailed what we're doing. I'll follow up with an email