Largely refactored onItemUse

Encapsulated prospecting results. Used one hash map instead of two array lists. Avoided creating large numbers of needless ItemStack instances. Avoided running code that doesn't have to, e.g. when false negatives are shown. Moved chat messages to their own methods. Preserving the original mechanic. Simple time profiling shows it's considerably faster now, too. Possibly much more memory efficient as well.