Use square farthest from point algorithm only for boxes

The x+y algorithm caused issues when detecting bubbles since their
corners aren't necessarily farthest in both x and y, it's more of a
diagonal across the ellipse. Use the old sqrt(x^2+y^2) algorithm for the
bubbles and the new x+y square-ish algorithm for detecting the boxes.
Build in Debug mode in Qt Creator by default

We'll want the pretty debug image output and if anybody tries debugging
it in release mode, they may have a few surprises.