Fix for Unity 2018.1 (#54)

* Merged in changes from MicroGSD/master

* - Added support for Unity 2018.1+
- Modified unit tests to display execution time and improved test performance (removed multiple GameObject.Find calls)
- Added Clean up tests to RoadArchitect->Testing menu

* Remove meta files for missing/unused assets

* Add missing .meta files

* Fix for wrong Unity version symbol in GSDRoadUtil.cs causing exception in Unity 2018.1.x
Remove meta file for directory that doesn't exist on import

GSDRootUtil.cs

@@ -73,7 +73,7 @@ public static string GetPrefabString(GameObject tObj){
 			if(tObj != null){
 				tString = UnityEditor.AssetDatabase.GetAssetPath( tObj );
 				if(tString == null || tString.Length < 1){
-#if UNITY_2018_1_OR_NEWER
+#if UNITY_2018_2_OR_NEWER
                     Object parentObject = UnityEditor.PrefabUtility.GetCorrespondingObjectFromSource(tObj); 
 #else
                     Object parentObject = UnityEditor.PrefabUtility.GetPrefabParent(tObj);