Fix a minor error in the health command

Woops, my bad!
Doesn't seem to be a disruptive error, just throws a stacktrace and
moves on (according to the user who found it)
Fix a minor error with the Projectile Hits event

Arrows: Powered by dark magic.
Add ItemPlantgrowth property

Plant growth is currently handled rather poorly by Bukkit...
nonetheless, here's a working property for it!
Merge branch 'master' of https://github.com/Morphan1/Denizen
Fix meta errors