fix: add scaling with hbox instead of border pane

Removed the border pane and switched tha root pane to a scroll bar pane which creates scrollbars when the window gets too small. Then added an Hbox to fit in three Vboxes of equal size. The unit lists on the right and left side have a max height of 500. The lists will scale up to that point. Since the Vboxes are set to have their children set to center, the army text won't be to high on when the window is on the larger side.

closes: #14 (closed)