stack-tastic

I added a selector pop-up window for stacks of units. Now you can see how many units are in a stack:

Above, there's a jet fighter "north" of a stack of three units. In the stack are two tanks and one other jet fighter. What happens if that jet fighter moves "south" one square?

As you can see, the stack layout changes to show the additional jet fighter, and the stack display now reads "4" instead of "3".

Clicking again, you get a popup unit selector:

Click on one of the tanks  in the popup, which selects the tank so you can move it: