Expose and document various APIs of Visject for plugins to use

Source/Editor/Surface/BehaviorTreeSurface.cs

@@ -31,7 +31,7 @@ namespace FlaxEditor.Surface
             var editor = Editor.Instance;
             var style = SurfaceStyle.CreateStyleHandler(editor);
             style.DrawBox = DrawBox;
-            style.DrawConnection = DrawConnection;
+            style.DrawConnection = SurfaceStyle.DrawStraightConnection;
             return style;
         }
 
@@ -49,11 +49,6 @@ namespace FlaxEditor.Surface
             Render2D.FillRectangle(rect, color);
         }
 
-        private static void DrawConnection(Float2 start, Float2 end, Color color, float thickness)
-        {
-            Archetypes.Animation.StateMachineStateBase.DrawConnection(ref start, ref end, ref color);
-        }
-
         private void OnActiveContextMenuVisibleChanged(Control activeCM)
         {
             _nodesCache.Wait();