Clean up solution (#912)

- Use global.json to control what version of .NET SDK is used for building so local builds also use the version used for pipeline builds
- Add some missing items to the sln so they are viewable through VS
- Delete extra project file

global.json

@@ -0,0 +1,8 @@
+{
+    "sdk": {
+        "version": "2.2.108"
+    },
+    "msbuild-sdks": {
+        "Microsoft.Build.Traversal": "2.0.2"
+    }
+}