Test directory refactoring step 1.

Moving TestProjects and TestPackages under root 'TestAssets' folder.

Partial fix #1250

TestAssets/TestProjects/TestLibraryWithAnalyzer/NuGet.Config

@@ -0,0 +1,9 @@
+<?xml version="1.0" encoding="utf-8"?>
+<configuration>
+  <packageSources>
+    <!--To inherit the global NuGet package sources remove the <clear/> line below -->
+    <clear />
+    <add key="dotnet-core" value="https://dotnet.myget.org/F/dotnet-core/api/v3/index.json" />
+    <add key="api.nuget.org" value="https://api.nuget.org/v3/index.json" />
+  </packageSources>
+</configuration>

TestAssets/TestProjects/TestLibraryWithAnalyzer/Program.cs

@@ -0,0 +1,15 @@
+using System;
+
+namespace ConsoleApplication
+{
+    public class Program
+    {
+        public static void Main(string[] args)
+        {
+            Console.WriteLine("Hello World!");
+        }
+    }
+
+    public class TT : Attribute
+    {}
+}

TestAssets/TestProjects/TestLibraryWithAnalyzer/project.json

@@ -0,0 +1,15 @@
+{
+    "version": "1.0.0-*",
+    "compilationOptions": {
+        "emitEntryPoint": true
+    },
+
+    "dependencies": {
+        "NETStandard.Library": "1.0.0-rc2-23805",
+        "System.Runtime.Analyzers": { "version": "1.1.0", "type": "build" }
+    },
+
+    "frameworks": {
+        "dnxcore50": { }
+    }
+}