ItemUtils: Update damageItemInHand to use the Damageable ItemMeta API

[prokopyl]

The ItemUtils.damageItemInHand() method still uses damage values, and should use the Damageable ItemMeta instead.

[AmauryCarrade]

We may want to rename it damageItemInMainHand for consistency with Bukkit? Especially if we add a damageItemInOffHand.

[prokopyl]

Either that, or considering the item is actually given to the method for damaging/breaking, it can probably just figure it out?

Actually, now that I look at it, the damageItemInHand doesn't seem to care if the item is in the player's hand or not. So it should probably be renamed instead?

[AmauryCarrade]

I think ItemUtils.damageItem() would suffice, yes. At the beginning, I thought that the method automatically took the object in hand, if there was one (bad memory...).