Changed Reset Event

Changed the event we use to trigger ArenaRegistry.reset() so that it
occurs earlier during server initialization. Also renamed reset() to
clear() to be a bit more clearer on its role. Made some minor spacing
changes to BlockArenaStarter.
Fixed NPE in TileEntityArenaSpawner

Fixed our problem with TileEntityArenaSpawner causing a crash. Now mobs
finally spawn properly. Also tweaked the mobs a little.