Closer to xplat build working

- Use newer nuget feed
- Lift versions to get new implementations
- Removed more dead code

NuGet.Config

@@ -3,7 +3,7 @@
   <packageSources>
     <!--To inherit the global NuGet package sources remove the <clear/> line below -->
     <clear />
-    <add key="dotnet-core" value="https://www.myget.org/F/dotnet-core-rel/api/v2" />
+    <add key="dotnet-core" value="https://www.myget.org/F/dotnet-core/api/v3/index.json" />
     <add key="AspNetCIDev" value="https://www.myget.org/F/aspnetcidev/api/v3/index.json" />
     <add key="roslyn-nightly" value="https://www.myget.org/F/roslyn-nightly/api/v3/index.json" />
     <add key="api.nuget.org" value="https://api.nuget.org/v3/index.json" />

src/Microsoft.Extensions.ProjectModel/Compilation/LibraryExporter.cs

@@ -207,8 +207,6 @@ namespace Microsoft.Extensions.ProjectModel.Compilation
 
         private IEnumerable<string> GetSharedSources(PackageDescription package)
         {
-            var directory = Path.Combine(package.Path, "shared");
-
             return package
                 .Library
                 .Files

src/Microsoft.Extensions.ProjectModel/project.json

@@ -12,6 +12,7 @@
     "System.Runtime.InteropServices.RuntimeInformation": "4.0.0-*",
 
     "NuGet.Packaging": "3.2.0",
+    "System.Security.Cryptography.Algorithms": "4.0.0-*",
 
     "Microsoft.Extensions.FileSystemGlobbing": "1.0.0-*",
     "Microsoft.Extensions.JsonParser.Sources": {