Master node improvements part 1

- Add two sided option
- Add multiply blend mode
- Rename blend modes
- Add master node parameter labels

com.unity.shadergraph/Editor/Data/LightweightPipeline/LightWeightPBRSubShader.cs

             subShader.Indent();
             subShader.AddShaderChunk("Tags{ \"RenderPipeline\" = \"LightweightPipeline\"}", true);
 
-            var materialOptions = ShaderGenerator.GetMaterialOptionsFromAlphaMode(masterNode.alphaMode);
+            var materialOptions = ShaderGenerator.GetMaterialOptions(masterNode.alphaMode, masterNode.twoSided.isOn);
             var tagsVisitor = new ShaderGenerator();
             materialOptions.GetTags(tagsVisitor);
             subShader.AddShaderChunk(tagsVisitor.GetShaderString(0), true);

com.unity.shadergraph/Editor/Data/LightweightPipeline/LightWeightUnlitSubShader.cs

             subShader.Indent();
             subShader.AddShaderChunk("Tags{ \"RenderType\" = \"Opaque\" \"RenderPipeline\" = \"LightweightPipeline\"}", true);
 
-            var materialOptions = ShaderGenerator.GetMaterialOptionsFromAlphaMode(masterNode.alphaMode);
+            var materialOptions = ShaderGenerator.GetMaterialOptions(masterNode.alphaMode, masterNode.twoSided.isOn);
             var tagsVisitor = new ShaderGenerator();
             materialOptions.GetTags(tagsVisitor);
             subShader.AddShaderChunk(tagsVisitor.GetShaderString(0), true);

com.unity.shadergraph/Editor/Data/MasterNodes/AlphaMode.cs

     public enum AlphaMode
     {
         Opaque,
-        AlphaBlend,
-        AdditiveBlend
+        Fade,
+        Additive,
+        Multiply
     }
 }

com.unity.shadergraph/Editor/Data/MasterNodes/PBRMasterNode.cs

         [SerializeField]
         private Model m_Model = Model.Metallic;
 
-        [EnumControl("")]
+        [EnumControl("Workflow")]
         public Model model
         {
             get { return m_Model; }
         [SerializeField]
         private AlphaMode m_AlphaMode;
 
-        [EnumControl("")]
+        [EnumControl("Blending")]
         public AlphaMode alphaMode
         {
             get { return m_AlphaMode; }
                     return;
 
                 m_AlphaMode = value;
+                Dirty(ModificationScope.Graph);
+            }
+        }
+
+        [SerializeField]
+        private bool m_TwoSided;
+
+        [ToggleControl("Two Sided")]
+        public Toggle twoSided
+        {
+            get { return new Toggle(m_TwoSided); }
+            set
+            {
+                if (m_TwoSided == value.isOn)
+                    return;
+                m_TwoSided = value.isOn;
                 Dirty(ModificationScope.Graph);
             }
         }

com.unity.shadergraph/Editor/Data/MasterNodes/UnlitMasterNode.cs

         [SerializeField]
         private AlphaMode m_AlphaMode;
 
-        [EnumControl("")]
+        [EnumControl("Blending")]
         public AlphaMode alphaMode
         {
             get { return m_AlphaMode; }
                     return;
 
                 m_AlphaMode = value;
+                Dirty(ModificationScope.Graph);
+            }
+        }
+
+        [SerializeField]
+        private bool m_TwoSided;
+
+        [ToggleControl("Two Sided")]
+        public Toggle twoSided
+        {
+            get { return new Toggle(m_TwoSided); }
+            set
+            {
+                if (m_TwoSided == value.isOn)
+                    return;
+                m_TwoSided = value.isOn;
                 Dirty(ModificationScope.Graph);
             }
         }

com.unity.shadergraph/Editor/Data/Util/ShaderGenerator.cs

             return res;
         }
 
-        public static SurfaceMaterialOptions GetMaterialOptionsFromAlphaMode(AlphaMode alphaMode)
+        public static SurfaceMaterialOptions GetMaterialOptions(AlphaMode alphaMode, bool twoSided)
         {
             var materialOptions = new SurfaceMaterialOptions();
             switch (alphaMode)
                     materialOptions.dstBlend = SurfaceMaterialOptions.BlendMode.Zero;
-                    materialOptions.cullMode = SurfaceMaterialOptions.CullMode.Back;
+                    materialOptions.cullMode = twoSided ? SurfaceMaterialOptions.CullMode.Off : SurfaceMaterialOptions.CullMode.Back;
-                case AlphaMode.AlphaBlend:
+                case AlphaMode.Fade:
-                    materialOptions.cullMode = SurfaceMaterialOptions.CullMode.Back;
+                    materialOptions.cullMode = twoSided ? SurfaceMaterialOptions.CullMode.Off : SurfaceMaterialOptions.CullMode.Back;
-                case AlphaMode.AdditiveBlend:
+                case AlphaMode.Additive:
-                    materialOptions.cullMode = SurfaceMaterialOptions.CullMode.Back;
+                    materialOptions.cullMode = twoSided ? SurfaceMaterialOptions.CullMode.Off : SurfaceMaterialOptions.CullMode.Back;
+                    materialOptions.zTest = SurfaceMaterialOptions.ZTest.LEqual;
+                    materialOptions.zWrite = SurfaceMaterialOptions.ZWrite.Off;
+                    materialOptions.renderQueue = SurfaceMaterialOptions.RenderQueue.Transparent;
+                    materialOptions.renderType = SurfaceMaterialOptions.RenderType.Transparent;
+                    break;
+                case AlphaMode.Multiply:
+                    materialOptions.srcBlend = SurfaceMaterialOptions.BlendMode.DstColor;
+                    materialOptions.dstBlend = SurfaceMaterialOptions.BlendMode.Zero;
+                    materialOptions.cullMode = twoSided ? SurfaceMaterialOptions.CullMode.Off : SurfaceMaterialOptions.CullMode.Back;
                     materialOptions.zTest = SurfaceMaterialOptions.ZTest.LEqual;
                     materialOptions.zWrite = SurfaceMaterialOptions.ZWrite.Off;
                     materialOptions.renderQueue = SurfaceMaterialOptions.RenderQueue.Transparent;