Fixes and minor enhancements for sub editor

- Zoom now works relative to the mouse's position rather than the center of the screen, much like Valve's Hammer Editor (or pulsegun's map editor shameless plug ;) )
- Rectangles now have line widths dependent on the camera zoom, not perfect but it's better than having lines disappear
- Fixed background resizing
- Fixed editor being completely broken because of no vsync, might still have a few bugs here and there
- Fixed selection rectangle not rendering at all when dragging from bottom right to top left
- Newline change in Item.cs

Subsurface/Source/Map/Structure.cs

@@ -143,8 +143,24 @@ namespace Barotrauma
             }
             set
             {
+                Rectangle oldRect = Rect;
                 base.Rect = value;
                 if (prefab.HasBody) CreateSections();
+                else
+                {
+                    foreach (WallSection sec in sections)
+                    {
+                        Rectangle secRect = sec.rect;
+                        secRect.X -= oldRect.X; secRect.Y -= oldRect.Y;
+                        secRect.X *= value.Width; secRect.X /= oldRect.Width;
+                        secRect.Y *= value.Height; secRect.Y /= oldRect.Height;
+                        secRect.Width *= value.Width; secRect.Width /= oldRect.Width;
+                        secRect.Height *= value.Height; secRect.Height /= oldRect.Height;
+                        secRect.X += value.X; secRect.Y += value.Y;
+                        sec.rect = secRect;
+                    }
+                }
+                
             }
         }