change automatic rendering behavior after resizing

[technogeeky]

I quote:

• the removal of the auto-render of the big map when you stop resizing it, reduces the jiggle-lag time if you just want to temporarily narrow it a bit for example (Thourion)

I add: this needs to be dealt with anyway. This will either go the route he's suggesting, or continue the behavior that exists now but is bugged (cache resize bug).

[5hipHappens]

I like the idea of a cache of the map. It could also be used when you start up the big map so you can see the something as soon as you open the map.