Bugfix for MinDHeap, new class called CountingMinDHeap which counts how many of each element it has.
Contains for the heap classes.
Bugfixes for MinDHeap. HeuristicGraph now uses CountingMinDHeap instead of PQueue.

Also better error reporting for NewGameSetupScene.
Slight optimization of d for the heap used by HeuristicGraph.
Updated UninformedGraph to use the new heap as well.
Removed PQueue because it's now obsolete.

Let's be honest, it was a pretty bad way to make a priority queue.