De-prioritize foreground trees when clicking something behind

[h.q.droid]

When hovering over something behind a non-fruit tree, the game should select the thing behind by default. One can always chop that useless tree at its bottom. This problem is bigger on Gleba than Nauvis because there are more types of trees, and there are usually large empty spaces in agricultural tower related blueprints which won't auto-chop trees when placed.