HDRenderPipeline: Add support for defaultShader

Assets/ScriptableRenderPipeline/HDRenderPipeline/Editor/HDRenderPipelineInspector.cs

         {
             public static GUIContent defaults = new GUIContent("Defaults");
             public static GUIContent defaultDiffuseMaterial = new GUIContent("Default Diffuse Material", "Material to use when creating objects");
+            public static GUIContent defaultShader = new GUIContent("Default Shader", "Shader to use when creating materials");
 
             public readonly GUIContent settingsLabel = new GUIContent("Settings");
 
         }
 
         private SerializedProperty m_DefaultDiffuseMaterial;
+        private SerializedProperty m_DefaultShader;
 
         // Display Debug
         SerializedProperty m_ShowMaterialDebug = null;
         private void InitializeProperties()
         {
             m_DefaultDiffuseMaterial = serializedObject.FindProperty("m_DefaultDiffuseMaterial");
+            m_DefaultShader = serializedObject.FindProperty("m_DefaultShader");
 
             // DebugDisplay debug
             m_DebugOverlayRatio = FindProperty(x => x.debugDisplaySettings.debugOverlayRatio);
             EditorGUILayout.LabelField(Styles.defaults, EditorStyles.boldLabel);
             EditorGUI.indentLevel++;
             EditorGUILayout.PropertyField(m_DefaultDiffuseMaterial, Styles.defaultDiffuseMaterial);
+            EditorGUILayout.PropertyField(m_DefaultShader, Styles.defaultShader);
             EditorGUI.indentLevel--;
 
             DebuggingUI(renderContext, renderpipelineInstance);

Assets/ScriptableRenderPipeline/HDRenderPipeline/HDRenderPipeline.asset

     enabled: 1
     shadowAtlasWidth: 4096
     shadowAtlasHeight: 4096
-    maxShadowDistance: 1000
+    maxShadowDistance: 400
     directionalLightCascadeCount: 4
     directionalLightCascades: {x: 0.05, y: 0.2, z: 0.3}
     directionalLightNearPlaneOffset: 5
   m_SkySettings: {fileID: 0}
   m_DefaultDiffuseMaterial: {fileID: 2100000, guid: 73c176f402d2c2f4d929aa5da7585d17,
     type: 2}
+  m_DefaultShader: {fileID: 4800000, guid: 6e4ae4064600d784cac1e41a9e6f2e59, type: 3}

Assets/ScriptableRenderPipeline/HDRenderPipeline/HDRenderPipeline.cs

         }
 
         [SerializeField] private Material m_DefaultDiffuseMaterial;
+        [SerializeField] private Shader m_DefaultShader;
+        }
+        public override Shader GetDefaultShader()
+        {
+            return m_DefaultShader;
         }
 
         public override Material GetDefaultMaterial()