Added rising costs

Buttons now take an additional argument, a bool, for determining if the
costs will rise by 10% each time an item is bought. Base costs are saved
to make it easier to recalculate when something is sold, to be added
later.
Rising costs fixed

Changed buttons to allow the costs to rise by a given percentage instead
of at a fixed 10%. Also added labels for the cost of each button next to
them.