Remove IObservableDescription.

It is superseded by IDescription.

Perspex.Base/IObservableDescription.cs

@@ -1,13 +0,0 @@
-// -----------------------------------------------------------------------
-// <copyright file="IObservableDescription.cs" company="Steven Kirk">
-// Copyright 2014 MIT Licence. See licence.md for more information.
-// </copyright>
-// -----------------------------------------------------------------------
-
-namespace Perspex
-{
-    public interface IObservableDescription
-    {
-        string Description { get; }
-    }
-}

Perspex.Base/Perspex.Base.csproj

@@ -46,7 +46,6 @@
     <Compile Include="Diagnostics\PerspexPropertyValue.cs" />
     <Compile Include="IDescription.cs" />
     <Compile Include="Collections\PerspexListExtensions.cs" />
-    <Compile Include="IObservableDescription.cs" />
     <Compile Include="Collections\IPerspexReadOnlyList.cs" />
     <Compile Include="PerspexObject.cs" />
     <Compile Include="PerspexProperty.cs" />
@@ -57,6 +56,7 @@
     <Compile Include="PriorityLevel.cs" />
     <Compile Include="PriorityValue.cs" />
     <Compile Include="Properties\AssemblyInfo.cs" />
+    <Compile Include="Reactive\PerspexObservable.cs" />
     <Compile Include="Threading\Dispatcher.cs" />
     <Compile Include="Threading\DispatcherPriority.cs" />
     <Compile Include="Threading\DispatcherTimer.cs" />