Handle removing entity while ticking. Fixes BUKKIT-1331

If a plugin causes an entity to be removed from the world while the
world is ticking entities the ticking loop gets out of sync and fails due
to trying to go beyond the end of the entity array. To ensure this doesn't
happen we store the loop position as a field so we can fix it up in the
entity remove method just like the tick method does when it removes an
entity.
Readd diff missed in the 1.7 update.
Hide message from connection throttle on startup. Fixes BUKKIT-5403
Rename Minecraft command permission nodes to meet fallback spec.
Add PlayerSelector.java for diff visibility.
Ignore player selectors if not a Command Block.
Update/improve configuration documentation.
Check if entity is in list before decrementing. Fixes BUKKIT-5404
Updated version to 1.7.2-R0.3 in pom.xml for Beta.
Updated version to 1.7.2-R0.4-SNAPSHOT for development towards next release.
Remove chunks from queue if we don't need them anymore.