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.
Using the ore name as key in the hash map

Overlooked that the 3 ore blocks use different meta values to determine what ore it is, using the blockID as key in the hash map would've introduced a bug. Using the ore's name as before instead.
Removed unused import ArrayList.
Merge pull request #320 from dmon82/Refactor

Largely refactored onItemUse