This code will always add a layer if either it was saved 'on', or it by default is 'on' - a layer that by default is 'on' but saved 'off' would start 'on' every time. Only a default 'off' layer would be restored correctly.

What we want is something more like:
```
  //if there's a saved state, use it instead of the default
  if ( typeof(overlayStatus[name]) !== 'undefined' ) defaultDisplay = overlayStatus[name];
  if ( defaultDisplay ) map.addLayer (...)
```