Undo support for all node controls

MaterialGraphProject/Assets/NewNodes/Editor/Keep/GradientNode.cs

 
 namespace UnityEngine.MaterialGraph
 {
-    [Title("Procedural/Gradient Editor")]
+    [Title("Input/Gradient")]
     public class GradientNode : AbstractMaterialNode, IGeneratesBodyCode
     {
         Gradient m_Gradient;

MaterialGraphProject/Assets/UnityShaderEditor/Editor/Drawing/Controls/EnumControl.cs

             {
                 value = EditorGUILayout.EnumPopup(m_Label, value);
                 if (changeCheckScope.changed)
+                {
+                    m_Node.owner.owner.RegisterCompleteObjectUndo("Change " + m_Node.name);
+                }
             }
         }
     }

MaterialGraphProject/Assets/UnityShaderEditor/Editor/Drawing/Controls/GradientControl.cs

                 EditorGUILayout.PropertyField(m_SerializedProperty, m_Label, true, null);
                 m_SerializedObject.ApplyModifiedProperties();
                 if (changeCheckScope.changed)
+                {
+                    m_Node.owner.owner.RegisterCompleteObjectUndo("Change " + m_Node.name);
+                }
             }
 
             var e = Event.current;
                 m_PropertyInfo.SetValue(m_Node, m_GradientObject.gradient, null);
                 m_PrevWindow = EditorWindow.focusedWindow.ToString();
-                Debug.Log("Update Gradient Shader");
             }
         }
     }

MaterialGraphProject/Assets/UnityShaderEditor/Editor/Drawing/Controls/ObjectControl.cs

             {
                 value = EditorGUILayout.MiniThumbnailObjectField(m_Label, value, m_PropertyInfo.PropertyType);
                 if (changeCheckScope.changed)
+                {
+                    m_Node.owner.owner.RegisterCompleteObjectUndo("Change " + m_Node.name);
+                }
             }
         }
     }

MaterialGraphProject/Assets/UnityShaderEditor/Editor/Drawing/Controls/PropertyControl.cs

             {
                 var value = EditorGUILayout.Popup("Property", currentSelectedIndex, properties.Select(x => x.displayName).ToArray());
                 if (changeCheckScope.changed)
+                {
+                    m_Node.owner.owner.RegisterCompleteObjectUndo("Change " + m_Node.name);
+                }
             }
         }
     }