Move primitive types into their own nuget package

[AdmiralSnyder]

Primitives, like System.Windows.Point should be moved into a standalone Nuget package. They shouldn't be tied to WPF.
System.Drawing.Primities exists as a reference point. This would allow usage outside WPF.

That way, it's possible to reference them from libraries without having to put UseWPF into the .csproj files (keeping them small, as e.g. test projects testing the algorithms apart form their UI implementation should be)

[lindexi]

@AdmiralSnyder Yeah, I do it in https://github.com/dotnet-campus/dotnetCampus.WPFType