sln reader/writer (#4870)

* Snap of sln reader/writer from https://github.com/mono/monodevelop

* Remove unnecessary code

* Create a new test asset with an sln file because adding an sln to an existing one broke other tests

* Remove commented out line

* Removing unneeded PropertyGroup per PR comments

* Update the license

* Fixing the license

TestAssets/TestProjects/TestAppWithSln/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/TestAppWithSln/TestAppWithSln.sln

@@ -0,0 +1,22 @@
+
+Microsoft Visual Studio Solution File, Format Version 12.00
+# Visual Studio 14
+VisualStudioVersion = 14.0.25420.1
+MinimumVisualStudioVersion = 10.0.40219.1
+Project("{8BB2217D-0F2D-49D1-97BC-3654ED321F3B}") = "TestAppWithSln", "TestAppWithSln.xproj", "{0138CB8F-4AA9-4029-A21E-C07C30F425BA}"
+EndProject
+Global
+	GlobalSection(SolutionConfigurationPlatforms) = preSolution
+		Debug|Any CPU = Debug|Any CPU
+		Release|Any CPU = Release|Any CPU
+	EndGlobalSection
+	GlobalSection(ProjectConfigurationPlatforms) = postSolution
+		{0138CB8F-4AA9-4029-A21E-C07C30F425BA}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{0138CB8F-4AA9-4029-A21E-C07C30F425BA}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{0138CB8F-4AA9-4029-A21E-C07C30F425BA}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{0138CB8F-4AA9-4029-A21E-C07C30F425BA}.Release|Any CPU.Build.0 = Release|Any CPU
+	EndGlobalSection
+	GlobalSection(SolutionProperties) = preSolution
+		HideSolutionNode = FALSE
+	EndGlobalSection
+EndGlobal

TestAssets/TestProjects/TestAppWithSln/TestAppWithSln.xproj

@@ -0,0 +1,18 @@
+<?xml version="1.0" encoding="utf-8"?>
+<Project ToolsVersion="14.0.23107" DefaultTargets="Build" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
+  <PropertyGroup>
+    <VisualStudioVersion Condition="'$(VisualStudioVersion)' == ''">14.0.23107</VisualStudioVersion>
+    <VSToolsPath Condition="'$(VSToolsPath)' == ''">$(MSBuildExtensionsPath32)\Microsoft\VisualStudio\v$(VisualStudioVersion)</VSToolsPath>
+  </PropertyGroup>
+  <Import Project="$(VSToolsPath)\DNX\Microsoft.DNX.Props" Condition="'$(VSToolsPath)' != ''" />
+  <PropertyGroup Label="Globals">
+    <ProjectGuid>0138cb8f-4aa9-4029-a21e-c07c30f425ba</ProjectGuid>
+    <RootNamespace>TestAppWithContents</RootNamespace>
+    <BaseIntermediateOutputPath Condition="'$(BaseIntermediateOutputPath)'=='' ">..\..\..\artifacts\obj\$(MSBuildProjectName)</BaseIntermediateOutputPath>
+    <OutputPath Condition="'$(OutputPath)'=='' ">..\..\..\artifacts\</OutputPath>
+  </PropertyGroup>
+  <PropertyGroup>
+    <SchemaVersion>2.0</SchemaVersion>
+  </PropertyGroup>
+  <Import Project="$(VSToolsPath)\DNX\Microsoft.DNX.targets" Condition="'$(VSToolsPath)' != ''" />
+</Project>

TestAssets/TestProjects/TestAppWithSln/project.json

@@ -0,0 +1,25 @@
+{
+  "version": "1.0.0-*",
+  "buildOptions": {
+    "emitEntryPoint": true
+  },
+  "dependencies": {
+    "Microsoft.NETCore.App": "1.0.1"
+  },
+  "frameworks": {
+    "netcoreapp1.0": {}
+  },
+  "runtimes": {
+    "win7-x64": {},
+    "win7-x86": {},
+    "osx.10.10-x64": {},
+    "osx.10.11-x64": {},
+    "ubuntu.14.04-x64": {},
+    "ubuntu.16.04-x64": {},
+    "centos.7-x64": {},
+    "rhel.7.2-x64": {},
+    "debian.8-x64": {},
+    "fedora.23-x64": {},
+    "opensuse.13.2-x64": {}
+  }
+}