Added a way for admins to fix up balances


My database managed to get into a state inconsistent with the wallet. I'm running on BukkitForge instead of CraftBukkit, and I suspect incoming transactions may not be triggering the appropriate listeners. So, I added admin /credit and /debit commands to fix balances (and a report of current system balance in in-game units), and some more logging on incoming transactions to try and track down what's going on.