UI/FX: Modified several UI elements' placement and style

UI/FX: Updated more building sprites to new style

UI/FX: Powerups no longer show up on tiles you cannot build on [empty spots]

Change: The Counter Trigger now starts at 1

Change: Format for saving images is now: "SuperPixelDefense_<image_size>px_<date_string>.png"

Change: Code optimizations to improve performance of buildings