Fix map in IE by deferring Vector layer addition to page load (note that deferred...

Fix map in IE by deferring Vector layer addition to page load (note that deferred script running is _not_ the same as onload), also only add the Vector layer as required, so to save some overhead.
I've trimmed down the unrequired options on the layer, they're defaulted from the map.
Thanks firefishy for the report.