revert ea45d0f447af24115275234403202fe993e0d84c - portal clustering still has some advantages
note: window.Render.prototype.getLinkPixelLength not restored - should have been deleted as part of an earlier change
portal-names - use different delays for data loading updates and user events - improves performance
test: remove code that rendered stale map data tiles from cache before retrieving from the network - will try it for a while and see if it makes things noticably more responsive