Brimstone Invis

Potions to permanently toggle invisible/visible sulphur cubes. Crafting recipe:

``` - Potion of invisiblity - minecraft:potion, minecraft:sulfur, minecraft:water_bucket - Potion of cleansing - minecraft:potion, minecraft:sulfur, minecraft:milk_bucket ```

Potions apply NV and blindness (each amplified by 64) for 2 seconds. Sulphur cubes toggle invisiblity, all other mobs have standard effects.

In reality, any sulfur cube with NV amplified by 64 will gain permanent invisibility, and any SC with Blindness amplified by 64 will lose said invisibility. The potions simply give the required effects.