Move PackagedCommands to TestAssets.

Convert package-command-test.ps1 to an XUnit test.

TestAssets/TestProjects/AppWithDirectDependency/Program.cs

@@ -0,0 +1,12 @@
+using System;
+
+namespace ConsoleApplication
+{
+    public class Program
+    {
+        public static void Main(string[] args)
+        {
+            Console.WriteLine("Hello World!");
+        }
+    }
+}

TestAssets/TestProjects/AppWithDirectDependency/project.json

@@ -0,0 +1,17 @@
+{
+    "version": "1.0.0-*",
+    "compilationOptions": {
+        "emitEntryPoint": true
+    },
+
+    "testRunner": "must-be-specified-to-generate-deps",
+    
+    "dependencies": {
+        "NETStandard.Library": "1.0.0-rc2-23810",
+        "dotnet-hello": {"version": "1.0.0", "target": "package"}
+    },
+
+    "frameworks": {
+        "dnxcore50": { }
+    }
+}