Adds more functionality for LazyManyObjectsResolverBase - adding type list delegates for lazy resolution.

src/Umbraco.Core/ObjectResolution/ManyObjectsResolverBase.cs

@@ -320,7 +320,16 @@ namespace Umbraco.Core.ObjectResolution
 		{
 			return new WriteLock(_lock);
 		}
-		
+
+		/// <summary>
+		/// Returns an upgradeable read lock for use when reading/modifying collections
+		/// </summary>
+		/// <returns></returns>
+		protected UpgradeableReadLock GetUpgradeableReadLock()
+		{
+			return new UpgradeableReadLock(_lock);
+		}
+
 		/// <summary>
 		/// Throws an exception if resolution is frozen
 		/// </summary>