Added AddSub Blending mode.

Added Substance Designer AddSub Blending Mode.
Formula Add Sub:   2.0*s+d-1.0

MaterialGraphProject/Assets/Rinaldo/BlendModeNode.cs

                 }
             }
         }
-/*This is to overide input to be vector 3, not really necessary anymore*/
+/*This is to overide input to be vector 3, not really necessary */
 /*
         protected override MaterialSlot GetInputSlot1()
         {
             var outputString = new ShaderGenerator();
             switch (m_BlendMode)
             {
+                case BlendModesEnum.AddSub:
+                    outputString.AddShaderChunk(GetFunctionPrototype("arg1", "arg2"), false);
+                    outputString.AddShaderChunk("{", false);
+                    outputString.Indent();
+                    outputString.AddShaderChunk("return 2.0 * arg1 + arg2 - 1.0;", false);
+                    outputString.Deindent();
+                    outputString.AddShaderChunk("}", false);
+                    break;
                 case BlendModesEnum.Burn:
                     outputString.AddShaderChunk(GetFunctionPrototype("arg1", "arg2"), false);
                     outputString.AddShaderChunk("{", false);
                     outputString.AddShaderChunk("}", false);
                     break;
             }
-
             visitor.AddShaderChunk(outputString.GetShaderString(0), true);
         }
     }

MaterialGraphProject/Assets/Rinaldo/BlendModesEnum.cs

 {
     public enum BlendModesEnum
     {
+        AddSub,
         Burn,
         Darken,
         Difference,

MaterialGraphProject/Assets/Rinaldo/Editor/BlendModeNodePresenter.cs

  */
         public override float GetHeight()
         {
-            return 3 * (EditorGUIUtility.singleLineHeight + EditorGUIUtility.standardVerticalSpacing) + EditorGUIUtility.standardVerticalSpacing;
+            return EditorGUIUtility.singleLineHeight + EditorGUIUtility.standardVerticalSpacing + EditorGUIUtility.standardVerticalSpacing;
         }
     }