Handle delete via window and presenter rather than `MaterialGraphView`

MaterialGraphProject/Assets/UnityShaderEditor/Editor/Drawing/MaterialGraphEditWindow.cs

                 e.commandName == "Copy" && presenter.canCopy
                 || e.commandName == "Paste" && presenter.canPaste
                 || e.commandName == "Duplicate" && presenter.canDuplicate
-                || e.commandName == "Cut" && presenter.canCut))
+                || e.commandName == "Cut" && presenter.canCut
+                || (e.commandName == "Delete" || e.commandName == "SoftDelete") && presenter.canDelete))
             {
                 e.Use();
             }
                     presenter.Duplicate();
                 if (e.commandName == "Cut")
                     presenter.Cut();
+                if (e.commandName == "Delete" || e.commandName == "SoftDelete")
+                    presenter.Delete();
             }
         }
 

MaterialGraphProject/Assets/UnityShaderEditor/Editor/Drawing/Presenters/MaterialGraphPresenter.cs

             InsertCopyPasteGraph(graph);
         }
 
+        public bool canDelete
+        {
+            get { return canCopy; }
+        }
+
+        public void Delete()
+        {
+            RemoveElements(elements.OfType<MaterialNodePresenter>().Where(e => e.selected), elements.OfType<GraphEdgePresenter>().Where(e => e.selected));
+        }
+
         public override void AddElement(EdgePresenter edge)
         {
             Connect(edge.output as GraphAnchorPresenter, edge.input as GraphAnchorPresenter);

MaterialGraphProject/Assets/UnityShaderEditor/Editor/Drawing/Views/MaterialGraphView.cs

                     {Event.KeyboardEvent("a"), FrameAll},
                     {Event.KeyboardEvent("f"), FrameSelection},
                     {Event.KeyboardEvent("o"), FrameOrigin},
-                    {Event.KeyboardEvent("delete"), DeleteSelection},
                     {Event.KeyboardEvent("#tab"), FramePrev},
                     {Event.KeyboardEvent("tab"), FrameNext}
                 });
 
             var graphDataSource = GetPresenter<MaterialGraphPresenter>();
             graphDataSource.AddNode(node);
-        }
-
-        // TODO JOCE Remove the "new" here. Use the base class' impl
-        new EventPropagation DeleteSelection()
-        {
-            var presenter = GetPresenter<MaterialGraphPresenter>();
-            if (presenter == null)
-                return EventPropagation.Stop;
-
-            presenter.RemoveElements(
-                selection.OfType<MaterialNodeView>().Select(x => x.GetPresenter<MaterialNodePresenter>()),
-                selection.OfType<Edge>().Select(x => x.GetPresenter<GraphEdgePresenter>())
-                );
-
-            return EventPropagation.Stop;
         }
 
         public override void OnDataChanged()