Enable XLF-based localization

1. Add the XliffTasks package for all projects.
2. Automatically update XLF files during build on dev machines.
3. Opt-in to the .NET Core satellite assembly generation task.
4. Turn off localization for non-shipping projects by default.
5. Work around an issue in locale-neutral CTO generation.

build/Targets/Imports.targets

@@ -121,6 +121,12 @@
     </When>
   </Choose>
 
+  <!-- Settings for localization -->
+  <PropertyGroup>
+    <!-- Only turn on localization for shipping binaries. -->
+    <EnableXlfLocalization Condition="'$(NonShipping)' == 'true'">false</EnableXlfLocalization>
+  </PropertyGroup>
+
   <Choose>
     <When Condition="'$(SignAssembly)' == 'true'">
       <Choose>
@@ -300,6 +306,33 @@
     </VSIXSourceItem>
   </ItemDefinitionGroup>
 
+  <!--
+    This is a workaround for allowing neutral CTO resource produced from *.vsct to go in the main assembly.
+    We move the neutral *.cto file to be categorized as WithCulture=true,Culture=en to prevent the tools from falsely reporting:
+      error VSSDK1006: Two CTO files have the same Menus.ctmenu resource name.
+     Note that this categorization does not apply to the items that actually produce the .resources.dll and so it will
+     not cause an English satellite to be generated.
+     The documented way around this is to put all resources (including neutral/en) in satellites:
+       https://msdn.microsoft.com/en-us/library/ee943168.aspx
+       However, that has consequences we do not want:
+        - It breaks resx code-gen to *.designer.cs
+        - It causes extra dll loads in en case
+        - If we ever split satellites in to language packs, the english fallback satellites would become a special case.
+  -->
+  <Target Name="AssignEnCultureToNeutralCto" BeforeTargets="MergeCtoResource">
+    <ItemGroup>
+      <_GeneratedCTOFilesWithCulture Include="@(_GeneratedCTOFilesWithNoCulture)">
+        <Culture>en</Culture>
+        <WithCulture>true</WithCulture>
+      </_GeneratedCTOFilesWithCulture>
+      <_GeneratedCTOFilesWithNoCulture Remove="@(_GeneratedCTOFilesWithNoCulture)" />
+      <_ResourcesToMergeWithCTOWithCultureMetadata Condition="'%(WithCulture)' != 'true'">
+        <Culture>en</Culture>
+        <WithCulture>true</WithCulture>
+      </_ResourcesToMergeWithCTOWithCultureMetadata>
+    </ItemGroup>
+  </Target>
+
   <ImportGroup Condition="'$(ImportVSSDKTargets)' == 'true'">
     <Import Project="$(NuGetPackageRoot)\Microsoft.VSSDK.BuildTools\$(VisualStudioBuildToolsVersion)\build\Microsoft.VsSDK.BuildTools.targets" />
     <Import Project="$(VSToolsPath)\VSSDK\Microsoft.VsSDK.targets" />

build/Targets/Packages.props

@@ -230,6 +230,7 @@
     <VSSDKComponentModelHostVersion>12.0.4</VSSDKComponentModelHostVersion>
     <VsWebsiteInteropVersion>8.0.0.0-alpha</VsWebsiteInteropVersion>
     <vswhereVersion>1.0.71</vswhereVersion>
+    <XliffTasksVersion>0.2.0-beta-000080</XliffTasksVersion>
     <xunitVersion>2.2.0</xunitVersion>
     <xunitanalyzersVersion>0.5.0</xunitanalyzersVersion>
     <xunitassertVersion>2.2.0</xunitassertVersion>

build/Targets/Settings.props

@@ -140,6 +140,16 @@
     <DeterministicSourceRoot Condition="'$(DeveloperBuild)' != 'true'">/_/</DeterministicSourceRoot>
 
     <EnableSourceLink Condition="'$(DeveloperBuild)' != 'true'">true</EnableSourceLink>
+
+    <!-- It is only intended to automatically run update during dev cycle. However, It will fail the build on CI if the XLF file is not updated.
+         XLF file should be checked in and loc team will update the XLF it with translated version.
+    -->
+    <UpdateXlfOnBuild Condition="'$(DeveloperBuild)' == 'true'">true</UpdateXlfOnBuild>
+
+    <!-- Even when we're using the "desktop" version of MSBuild we always want to use the "Core" approach for generating satellite assemblies.
+         This avoids a couple of issues in al.exe (see https://github.com/dotnet/roslyn/issues/23190 and https://github.com/dotnet/roslyn/issues/23191
+         for details on those issues). -->
+    <GenerateSatelliteAssembliesForCore>true</GenerateSatelliteAssembliesForCore>
   </PropertyGroup>
 
   <!-- Windows specific settings -->
@@ -223,6 +233,10 @@
    -->
   <Import Project="$(ToolsetCompilerPropsFilePath)" Condition="Exists('$(ToolsetCompilerPropsFilePath)') AND '$(BootstrapBuildPath)' == '' AND '$(OS)' == 'Windows_NT'" />
 
+  <ItemGroup>
+    <PackageReference Include="XliffTasks" Version="$(XliffTasksVersion)" PrivateAssets="All" />
+  </ItemGroup>
+
   <!-- 
     Language specifc settings