Fix SemanticVersioning targets

[tautropfli]

Resolves #823

[FreeApophis]

NuGet generation fails with: error MSB4018: The "GenerateSemanticVersionRanges" task failed unexpectedly.

[tautropfli]

I decided to extract this into its own package. This makes the whole dependency thing a lot easier (I can pack NuGet.SemanticVersioning together with the task) and allows us to use it in other repos too :)

See: polyadic/build#1

[FreeApophis]

Still do not understand what it actually should do.

[tautropfli]

Still do not understand what it actually should do.

The goal or the implementation?

[FreeApophis]

I think I do not understand the goal, and therefore the implementation does not help.

[tautropfli]

Ah 😅

The goal is to reference Funcky using a semantic version range e.g. [3.5.0, 4) from the other NuGet packages in this repo instead of the default >=3.5.0.

The implementation does this by hooking into the pack process (that's what the Polyadic.Build.SemanticVersioning.targets file does).
It replaces the versions of each ProjectReference with an auto-generated range (that's what the GenerateSemanticVersionRanges is for).

[FreeApophis]

I see - the problem was not xUnit but the fact that it is project reference. No wonder I was confused. Approved and merged.