Simply adds the spelunker potion from Terraria.

The spelunker effect will highlight all ores in your surroundings. By default, this is a 16 block radius and is fully configurable in the configuration file. The potion can be brewed by using amethyst dust and a night vision potion. Amethyst dust drops with a 10% chance from amethyst clusters. It's also possible to find the potion in mineshafts with a 35% chance.