[UWP] Fixes for usage of XF with .net native toolchain (#1024)

* [UWP]Add required info for .net native when using AccessibilityView on UWP

* [UWP] Add reference to xaml assembly

* [UWP] Change rd.xml to be a embeded resource

* [UWP] Move code to the right place

* [UW]Only specify namespace we need

Xamarin.Forms.Platform.UAP/Properties/Xamarin.Forms.Platform.UAP.rd.xml

@@ -28,6 +28,7 @@
   <Library Name="Xamarin.Forms.Platform.UAP">
 
   	<!-- add directives for your library here -->
-
+    <Namespace Name="Windows.UI.Xaml.Automation.Peers" MarshalObject="Required All"/>
+  
   </Library>
 </Directives>

Xamarin.Forms.Platform.UAP/Xamarin.Forms.Platform.UAP.csproj

@@ -195,7 +195,7 @@
     <Compile Include="StepperControl.cs" />
     <Compile Include="TabbedPageRenderer.cs" />
     <Compile Include="ToolbarPlacementHelper.cs" />
-    <Content Include="Properties\Xamarin.Forms.Platform.UAP.rd.xml" />
+    <EmbeddedResource Include="Properties\Xamarin.Forms.Platform.UAP.rd.xml" />
     <Compile Include="..\Xamarin.Forms.Core\Properties\GlobalAssemblyInfo.cs">
       <Link>Properties\GlobalAssemblyInfo.cs</Link>
     </Compile>

Xamarin.Forms.Platform.WinRT/WindowsBasePlatformServices.cs

@@ -78,6 +78,10 @@ namespace Xamarin.Forms.Platform.WinRT
 			if (!assemblies.Contains(thisAssembly))
 				assemblies.Add(thisAssembly);
 
+			Assembly xamlAssembly = typeof(Xamarin.Forms.Xaml.IMarkupExtension).GetTypeInfo().Assembly;
+			if (!assemblies.Contains(xamlAssembly))
+				assemblies.Add(xamlAssembly);
+
 			return assemblies.ToArray();
 		}