SabreCSG generates warnings

[AzureBerylBlue]

Assets\SabreCSG\Scripts\Extensions\EditorHelper.cs(47,49): warning CS0618: 'SceneView.OnSceneFunc' is obsolete: 'OnSceneFunc() has been deprecated. Use System.Action instead.'
Assets\SabreCSG\Scripts\CSGModel.cs(1045,9): warning CS0618: 'PrefabUtility.GetPrefabObject(Object)' is obsolete: 'Use GetPrefabInstanceHandle for Prefab instances. Handles for Prefab Assets has been discontinued.'
Assets\SabreCSG\Scripts\Extensions\EditorHelper.cs(49,32): warning CS0618: 'SceneView.onSceneGUIDelegate' is obsolete: 'onSceneGUIDelegate has been deprecated. Use duringSceneGui instead.'

[AzureBerylBlue]

SabreCSG/Scripts/Extensions/EditorHelper.cs

Lines 44 to 50 in e27cda2

	/// <summary>
	/// DO NOT USE - only here for compatibility with old third party plugins!
	/// </summary>
	public static bool SceneViewHasDelegate(SceneView.OnSceneFunc targetDelegate)
	{
	return HasDelegate(SceneView.onSceneGUIDelegate, targetDelegate);
	}

Workaround: These lines can be safely deleted to make some of the warnings go away.
This plus pull request #253 make a clean warning free project.