Allow extracting framework-compatible DLLs from package #723

Nuget.Core has a method that lists all DLLs in a package:

public static IEnumerable<IPackageFile> GetLibFiles(this IPackage package);

You can then use another Nuget method to filter out only those DLLs that are relevant for a relevant version of the .NET framework:

 public static bool TryGetCompatibleItems<T>(FrameworkName projectFramework, IEnumerable<T> items, out IEnumerable<T> compatibleItems) where T : IFrameworkTargetable;

For example scriptcs uses these features to load Nuget packages by convention on startup. It would be cool if the same was available in the Paket API