Allow loading .msbuildproj in VS using NoTargets (#98)

By including the design-time targets and imports expected by CPS, we
allow the full loading and editing experience in the IDE automatically.

Fixes #97

Author: kzu

src/NoTargets/Sdk/Sdk.props

@@ -15,4 +15,8 @@
   <Import Project="Sdk.props" Sdk="Microsoft.NET.Sdk" Condition=" '$(MicrosoftCommonPropsHasBeenImported)' != 'true' "/>
 
   <Import Project="$(CustomAfterNoTargetsProps)" Condition=" '$(CustomAfterNoTargetsProps)' != '' And Exists('$(CustomAfterNoTargetsProps)') " />
-</Project>
+
+  <!-- For CPS/VS support. Importing in .props allows any subsequent targets to redefine this if needed -->
+  <Target Name="CompileDesignTime" />
+  
+</Project>

src/NoTargets/Sdk/Sdk.targets

@@ -43,5 +43,10 @@
     </CoreBuildDependsOn>
   </PropertyGroup>
 
+  <!-- For CPS/VS support. See https://github.com/dotnet/project-system/blob/master/src/Microsoft.VisualStudio.ProjectSystem.Managed/ProjectSystem/DesignTimeTargets/Microsoft.Managed.DesignTime.targets#L60 -->
+  <Import Project="$(MSBuildExtensionsPath)\Microsoft\VisualStudio\Managed\Microsoft.Managed.DesignTime.targets" 
+          Condition="'$(DebuggerFlavor)' == '' And Exists('$(MSBuildExtensionsPath)\Microsoft\VisualStudio\Managed\Microsoft.Managed.DesignTime.targets')" />
+
   <Import Project="$(CustomAfterNoTargets)" Condition="'$(CustomAfterNoTargets)' != '' and Exists('$(CustomAfterNoTargets)')" />
+  
 </Project>