Support NuGet packages that include DLLs
I ran into an issue attempting to use LINQPad to try out https://www.nuget.org/packages/libsodium-net/ - the package imported, but code failed with a DllNotFoundException. The package wraps a third-party DLL, which gets installed to a subdirectory of AppData\Local\LINQPad\NuGet.FW46. In Visual Studio, it apparently uses Baseclass.Contrib.Nuget.Output to copy the package output folder contents to the build folder. This doesn't work with LINQPad.