Fix P2P migration

Fixes #4269 by deep cloning the MsbuildTemplateProject for each P2P reference. Add test which migrates and builds P2P references.

TestAssets/TestProjects/TestAppDependencyGraph/CsprojLibrary3/CsprojLibrary3.csproj

@@ -0,0 +1,17 @@
+<Project ToolsVersion="14.0" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
+  <Import Project="$(MSBuildExtensionsPath)\$(MSBuildToolsVersion)\Microsoft.Common.props" />
+
+  <PropertyGroup>
+    <OutputType>Library</OutputType>
+    <TargetFrameworkIdentifier>.NETStandard</TargetFrameworkIdentifier>
+    <TargetFrameworkVersion>v1.5</TargetFrameworkVersion>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <Compile Include="**\*.cs" Exclude="$(GlobalExclude)" />
+    <EmbeddedResource Include="**\*.resx" Exclude="$(GlobalExclude)" />
+    <None Include="project.json" />
+  </ItemGroup>
+
+  <Import Project="$(MSBuildToolsPath)\Microsoft.CSharp.targets" />
+</Project>

TestAssets/TestProjects/TestAppDependencyGraph/CsprojLibrary3/Helper.cs

@@ -0,0 +1,15 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+
+using System;
+
+namespace TestLibrary
+{
+    public static class ProjectC
+    {
+        public static string GetMessage()
+        {
+            return "This string came from CsprojLibrary3";
+        }
+    }
+}

TestAssets/TestProjects/TestAppDependencyGraph/CsprojLibrary3/project.json

@@ -0,0 +1,11 @@
+{
+  "dependencies": {},
+  "frameworks": {
+    "netstandard1.5": {
+      "dependencies": {
+        "Microsoft.NETCore.Sdk": "1.0.0-alpha-20160923-4",
+        "NETStandard.Library": "1.6.0"
+      }
+    }
+  }
+}