Spawn monsters without prematurely exiting. Fixes BUKKIT-3425

By using return 0, we exit the loop prematurely preventing other
creature types from being spawned if one type is set to 0. By using
continue we move on to the other types and allow them to spawn
properly.
Add ItemStackMapTest

This test was missing from c056293b38cb9a1296937d91746b175252be044a
Throw BlockPlaceEvent when placing double slabs. Fixes BUKKIT-2469
Handle beds and doors the same way as other blocks. Fixes BUKKIT-3437
Relates to: BUKKIT-3438
Spigot
EMC POM changes
Remove CraftBukkit "Feature" of ItemStack's having infinite use.
Add 2 events for better control of mob spawning (Natural and Spawners)
Add PlayerUseItem Event so we can control when an item is consumed.
Make Items not have a repair cost increase due to Anvil usage.
Add Custom Timings to various points
Try old 1.4.5 dig speed algorithm for better results.
Fix blockStem modifier formula