Cleanup project structure

Restructured the project somewhat and cleaned up classes so that things are where they belong. Created "Helpers" folder and put appropriate helper classes in there.

Important things:
- The "GameObject path" methods are now extension methods on UnityEngine.Transform
- Removed AccessTools (Reflection helpers) as there was no use of it. Replaced with ReflectionHelpers class.
- Some improvements to the "Object Reflection" window, should be a bit faster now. Code cleaned up significantly.

src/MainMenu/MainMenu.cs

@@ -98,7 +98,7 @@ namespace Explorer
             {
                 CppExplorer.ArrayLimit = _lim;
             }
-            CppExplorer.Instance.MouseInspect = GUILayout.Toggle(CppExplorer.Instance.MouseInspect, "Inspect Under Mouse (Shift + RMB)", null);
+            InspectUnderMouse.EnableInspect = GUILayout.Toggle(InspectUnderMouse.EnableInspect, "Inspect Under Mouse (Shift + RMB)", null);
             GUILayout.EndHorizontal();
 
             GUILayout.BeginHorizontal(null);