Perspex.Win32 shouldn't reference types from WPF, that causes issues with Mono build

src/Windows/Perspex.Win32/Embedding/EmbeddedWindowImpl.cs

@@ -1,47 +1,14 @@
 namespace Perspex.Win32
 {
     using System;
-    using System.Collections.Generic;
-    using System.Linq;
-    using System.Runtime.InteropServices;
-    using System.Text;
-    using System.Threading.Tasks;
-    using System.Windows.Interop;
     using Perspex.Win32.Interop;
 
     public class EmbeddedWindowImpl : WindowImpl
     {
         private static readonly System.Windows.Forms.UserControl WinFormsControl = new System.Windows.Forms.UserControl();
 
-        public HwndHost Host { get; set; }
-
-        private class FakeHost : HwndHost
-        {
-            private readonly IntPtr hWnd;
-
-            public FakeHost(IntPtr hWnd)
-            {
-                this.hWnd = hWnd;
-            }
-
-            protected override HandleRef BuildWindowCore(HandleRef hwndParent)
-            {
-                UnmanagedMethods.SetParent(this.hWnd, hwndParent.Handle);
-                return new HandleRef(this, this.hWnd);
-            }
-
-            protected override void DestroyWindowCore(HandleRef hwnd)
-            {
-            }
-        }
-
         public IntPtr Handle { get; private set; }
 
-        public HwndHost CreateWpfHost()
-        {
-            return new FakeHost(this.Handle);
-        }
-
         protected override IntPtr CreateWindowOverride(ushort atom)
         {
             var hWnd = UnmanagedMethods.CreateWindowEx(

src/Windows/Perspex.Win32/Perspex.Win32.csproj

@@ -34,8 +34,6 @@
     <DocumentationFile>bin\Release\Perspex.Win32.XML</DocumentationFile>
   </PropertyGroup>
   <ItemGroup>
-    <Reference Include="PresentationCore" />
-    <Reference Include="PresentationFramework" />
     <Reference Include="Splat, Version=1.6.2.0, Culture=neutral, processorArchitecture=MSIL">
       <HintPath>..\..\..\packages\Splat.1.6.2\lib\Net45\Splat.dll</HintPath>
       <Private>True</Private>
@@ -62,7 +60,6 @@
     <Reference Include="System.Reactive.PlatformServices">
       <HintPath>..\..\..\packages\Rx-PlatformServices.2.2.5\lib\net45\System.Reactive.PlatformServices.dll</HintPath>
     </Reference>
-    <Reference Include="WindowsBase" />
   </ItemGroup>
   <ItemGroup>
     <Compile Include="..\..\Shared\SharedAssemblyInfo.cs">