Fix warnings in S.R.E & MEF tests

Commit migrated from https://github.com/dotnet/corefx/commit/b5a6e6963b7f0add7f8217769ed71197b92a3f7f

src/libraries/System.Composition/demos/Microsoft.Composition.Demos.ExtendedCollectionImports/Microsoft.Composition.Demos.ExtendedCollectionImports.csproj

@@ -5,6 +5,7 @@
     <ProjectGuid>{44C7E52C-3873-4C64-875C-8A23A8376D60}</ProjectGuid>
     <RootNamespace>Microsoft.Composition.Demos.ExtendedCollectionImports</RootNamespace>
     <AssemblyName>Microsoft.Composition.Demos.ExtendedCollectionImports</AssemblyName>
+    <NuGetTargetMoniker>.NETStandard,Version=v1.3</NuGetTargetMoniker>
   </PropertyGroup>
   <PropertyGroup Condition="'$(Configuration)|$(Platform)' == 'Debug|AnyCPU'" />
   <PropertyGroup Condition="'$(Configuration)|$(Platform)' == 'Release|AnyCPU'" />

src/libraries/System.Composition/demos/Microsoft.Composition.Demos.ExtendedCollectionImports/project.json

 {
   "dependencies": {
-    "Microsoft.NETCore.Platforms": "1.0.1",
     "System.Collections": "4.0.11",
     "System.Linq": "4.1.0",
     "System.Reflection": "4.1.0"
   },
   "frameworks": {
-    "netcoreapp1.0": {}
+    "netstandard1.3": {}
   }
 }
\ No newline at end of file

src/libraries/System.Composition/scenarios/TestLibrary/TestLibrary.csproj

@@ -5,6 +5,7 @@
     <ProjectGuid>{DA6841A5-0344-4CC7-98B0-89CBEE18DEE3}</ProjectGuid>
     <RootNamespace>TestLibrary</RootNamespace>
     <AssemblyName>TestLibrary</AssemblyName>
+    <NuGetTargetMoniker>.NETStandard,Version=v1.3</NuGetTargetMoniker>
   </PropertyGroup>
   <PropertyGroup Condition="'$(Configuration)|$(Platform)' == 'Debug|AnyCPU'" />
   <PropertyGroup Condition="'$(Configuration)|$(Platform)' == 'Release|AnyCPU'" />

src/libraries/System.Composition/scenarios/TestLibrary/project.json

 {
   "dependencies": {
-    "Microsoft.NETCore.Platforms": "1.0.1",
     "System.Runtime": "4.1.0"
   },
   "frameworks": {
-    "netcoreapp1.0": {}
+    "netstandard1.3": {}
   }
 }
\ No newline at end of file

src/libraries/System.Runtime.Extensions/tests/System.Runtime.Extensions.Tests.csproj

@@ -138,6 +138,7 @@
     <ProjectReference Include="TestApp\TestApp.csproj">
       <Project>{9F312D76-9AF1-4E90-B3B0-815A1EC6C346}</Project>
       <Name>TestApp</Name>
+      <UndefineProperties>TargetGroup;OSGroup</UndefineProperties>
     </ProjectReference>
     <!-- ToDo: Remove this P2P reference once new packages are produced and updated -->
     <ProjectReference Include="..\..\System.IO\pkg\System.IO.pkgproj" />

src/libraries/System.Runtime.Extensions/tests/TestApp/TestApp.csproj

@@ -8,6 +8,7 @@
     <AssemblyName>TestApp</AssemblyName>
     <AutoGenerateBindingRedirects>true</AutoGenerateBindingRedirects>
     <CopyNuGetImplementations>false</CopyNuGetImplementations>
+    <NuGetTargetMoniker Condition="'$(TargetGroup)' == ''">.NETStandard,Version=v1.3</NuGetTargetMoniker>
   </PropertyGroup>
   <!-- Default configurations to help VS understand the configurations -->
   <PropertyGroup Condition="'$(Configuration)|$(Platform)' == 'Debug|AnyCPU'" />

src/libraries/System.Runtime.Extensions/tests/TestApp/project.json

 {
   "dependencies": {
-    "Microsoft.NETCore.Platforms": "1.2.0-beta-24711-02",
     "System.Runtime": "4.4.0-beta-24711-02",
     "System.Runtime.Extensions": "4.4.0-beta-24711-02",
     "System.Resources.ResourceManager": "4.4.0-beta-24711-02",
@@ -9,8 +8,6 @@
     "System.Threading.Thread": "4.4.0-beta-24711-02"
   },
   "frameworks": {
-    ".NETCoreApp,Version=v1.0": {},
-    ".NETCoreApp,Version=v1.1": {},
-    "netstandard1.3": {}
+    "netstandard1.3": { }
   }
 }

src/libraries/System.Runtime.Extensions/tests/VoidMainWithExitCodeApp/VoidMainWithExitCodeApp.csproj

@@ -8,6 +8,7 @@
     <AssemblyName>VoidMainWithExitCodeApp</AssemblyName>
     <AutoGenerateBindingRedirects>true</AutoGenerateBindingRedirects>
     <CopyNuGetImplementations>false</CopyNuGetImplementations>
+    <NuGetTargetMoniker Condition="'$(TargetGroup)' == ''">.NETStandard,Version=v1.3</NuGetTargetMoniker>
   </PropertyGroup>
   <!-- Default configurations to help VS understand the configurations -->
   <PropertyGroup Condition="'$(Configuration)|$(Platform)' == 'Debug|AnyCPU'" />

src/libraries/System.Runtime.Extensions/tests/VoidMainWithExitCodeApp/project.json

 {
   "dependencies": {
-    "Microsoft.NETCore.Platforms": "1.2.0-beta-24711-02",
     "System.Runtime": "4.4.0-beta-24711-02",
     "System.Runtime.Extensions": "4.4.0-beta-24711-02",
     "System.Reflection": "4.4.0-beta-24711-02",
     "System.Threading.Thread": "4.4.0-beta-24711-02"
   },
   "frameworks": {
-    "netcoreapp1.0": {},
-    "netcoreapp1.1": {},
-    "netstandard1.5": {},
     "netstandard1.3": {}
   }
 }