Added basic transition system that works with GameApp's phases. Currently does a fade-out between elements, which works well in some places and not-so-well in others. We'll definitely want to think about where and where not to use it... they'd work a lot better if we could spawn a thread to handle loading the next state while transitioning.
Also cleaned up the shop a bit, so it uses ReadButton() instead of GetButtonClick()-- hence the slight change to JGE. Added a tiled image for the task board, which loads conservatively (I tried 128x128, but it didn't look as good).
