setup zoom behavior to use Mercator space
setup zoom behavior to use Mercator space

Also, a few optimizations:
* don't redraw the minimap unless mainmap dispatched a full redraw event
* don't recenter mainmap on zoomend unless minimap actually got panned

1ec5/iD,energiekollektiv/openmod.sh-id,morray/iD,energiekollektiv/openmod.sh-id,zbycz/iD,AndreasHae/iD,ngageoint/hootenanny-ui,zbycz/iD,morray/iD,ngageoint/hootenanny-ui,ngageoint/hootenanny-ui,bagage/iD,openstreetmap/iD,mapmeld/iD,andreic-telenav/iD,kartta-labs/iD,digidem/iD,mapmeld/iD,tbicr/iD,openstreetmap/iD,1ec5/iD,edpop/iD,bagage/iD,andreic-telenav/iD,kartta-labs/iD,1ec5/iD,AndreasHae/iD,kartta-labs/iD,tbicr/iD,kepta/iD,kepta/iD,digidem/iD,AndreasHae/iD,edpop/iD,mapmeld/iD,bagage/iD,edpop/iD,openstreetmap/iD