Added level browser

The level browser is finally here! Well, not really, this is just a demo version until I get a better GUI built. To save the current level, click on the textbox and press enter. It will then save your level and make an id for it. Be sure to write this down, as you can only see it once. To load a level, click on the textbox, enter the level id, and press enter. Then it will load the level. If it beeps during a save, it means it failed.