Makes ApplicationContext disposable so that 3rd party devs are able to reset their applications (or unit tests), updated

resolution and created a ResolverCollection to track all resolvers created so it's super easy to reset all of them at once
(which is what happens on ApplicationContext.Dispose. ApplicationContext.Dispose is also implicitly implemented as to not
show in intellisense that the Dispose method exists... must be cast to IDisposable to work.

src/Umbraco.Core/ObjectResolution/ResolverBase.cs

@@ -3,26 +3,52 @@ using System.Threading;
 
 namespace Umbraco.Core.ObjectResolution
 {
+    /// <summary>
+    /// Base non-generic class for resolvers
+    /// </summary>
+    public abstract class ResolverBase
+    {
+        protected ResolverBase(Action resetAction)
+        {
+            //add itself to the internal collection
+            ResolverCollection.Add(this, resetAction);
+        }
+        
+    }
+
 	/// <summary>
 	/// The base class for all resolvers.
 	/// </summary>
 	/// <typeparam name="TResolver">The type of the concrete resolver class.</typeparam>
 	/// <remarks>Provides singleton management to all resolvers.</remarks>
-	public abstract class ResolverBase<TResolver> 
-		where TResolver : class
+    public abstract class ResolverBase<TResolver> : ResolverBase
+        where TResolver : ResolverBase
 	{
-		static TResolver _resolver;
-		
-		/// <summary>
-		/// The lock for the singleton.
-		/// </summary>
-		/// <remarks>
-		/// Though resharper says this is in error, it is actually correct. We want a different lock object for each generic type.
-		/// See this for details: http://confluence.jetbrains.net/display/ReSharper/Static+field+in+generic+type
-		/// </remarks>
-		static readonly ReaderWriterLockSlim ResolversLock = new ReaderWriterLockSlim();
 
-		/// <summary>
+        /// <summary>
+        /// The underlying singleton object instance
+        /// </summary>
+        static TResolver _resolver;
+
+        /// <summary>
+        /// The lock for the singleton.
+        /// </summary>
+        /// <remarks>
+        /// Though resharper says this is in error, it is actually correct. We want a different lock object for each generic type.
+        /// See this for details: http://confluence.jetbrains.net/display/ReSharper/Static+field+in+generic+type
+        /// </remarks>
+        static readonly ReaderWriterLockSlim ResolversLock = new ReaderWriterLockSlim();
+
+        /// <summary>
+        /// Constructor set the reset action for the underlying object
+        /// </summary>
+	    protected ResolverBase()
+	        : base(() => Reset())
+	    {
+
+	    }
+
+	    /// <summary>
 		/// Gets or sets the resolver singleton instance.
 		/// </summary>
 		/// <remarks>The value can be set only once, and cannot be read before it has been set.</remarks>
@@ -84,15 +110,18 @@ namespace Umbraco.Core.ObjectResolution
             //In order to reset a resolver, we always must reset the resolution
             if (resetResolution)
             {                
-                Resolution.Reset();    
+                Resolution.Reset();
             }
-            
+
+            //ensure its removed from the collection
+            ResolverCollection.Remove(_resolver);
 
             using (Resolution.Configuration)
 			using (new WriteLock(ResolversLock))
 			{
 				_resolver = null;
 			}
+            
 		}
 	}
 }