Rework library structure to allow broader use

[HLWeil]

Hey,

I ran into your Repo searching for a GCN library (obviously). I think the approach you took with both Torchsharp.Fun and the gcn functions is pretty elegant. Unfortunately, everything's jammed into the exe.

For my purposes, I separated the types functions from the console app and made some namespace changes, moving everything into the Torchsharp.Fun namespace.

Do you think this might be applicable to this main repo too?