Fix Cascade.DeleteOrphan (#474)

+semver:fix

Author: hazzik

src/FluentNHibernate.Testing/DomainModel/Mapping/CascadeExpressionTester.cs

@@ -73,7 +73,7 @@ public void Refresh_should_add_the_correct_cascade_attribute_to_the_parent_part(
         [Test]
         public void DeleteOrphans_should_add_the_correct_cascade_attribute_to_the_parent_part()
         {
-            A_call_to(_cascade.DeleteOrphans).should_set_the_cascade_value_to("delete-orphans");
+            A_call_to(_cascade.DeleteOrphan).should_set_the_cascade_value_to("delete-orphan");
         }
 
         [Test]

src/FluentNHibernate/Mapping/CascadeExpression.cs

@@ -88,9 +88,18 @@ public TParent Refresh()
         /// <summary>
         /// Cascade deletes orphans
         /// </summary>
+        [Obsolete("Please use DeleteOrphan instead")]
         public TParent DeleteOrphans()
         {
-            setter("delete-orphans");
+            return DeleteOrphan();
+        }
+
+        /// <summary>
+        /// Cascade deletes orphans
+        /// </summary>
+        public TParent DeleteOrphan()
+        {
+            setter("delete-orphan");
             return parent;
         }
 

src/FluentNHibernate/Mapping/CollectionCascadeExpression.cs

@@ -26,7 +26,7 @@ public CollectionCascadeExpression(TParent parent, Action<string> setter)
         /// <summary>
         /// Cascade deletes, deleting any orphaned records
         /// </summary>
-        public TParent DeleteOrphan()
+        public new TParent DeleteOrphan()
         {
             setter("delete-orphan");
             return parent;