Get closest item doesn't actually get closest item

[Ext3h]

With the greedy traversal approach in the Octtree, we often miss items which are actually close in favor of items which are merely in the same quadrant.

Especially close to the center of the map, this becomes quite obvious to the user, as even items on the neighboring tile tend to be ignored in favor of far more distance ones.

We have to switch the traversal to broad first search instead of greedy depth first.