Add support for clearing armor slot + Off Hand slot using /clearinventory

I'd like to see this one as well. Using this command for the prep phase of an arena, and I don't want people sneaking non-pvp-kit items into it.

Yeah, just did this in my own build, all you need to do is add a player.getInventory().setItemInOffHand(null); after player.getInventory().setArmorContents(null);

Too bad the new clear confirmation breaks my original purpose for this command (clear inventory upon clicking a button to enter an arena), so guess I'll have to get rid of that as well :/

You can already clear armor slots with /clear ** but the offhand slot should be included.