Fix THORNS now will not activate the activator PLAYER_CLICK_ENTITY when an entity hit you

Fix a problem with placeholders now you can use them correctly in Mythic mobs command, and you can seperate multiple placeholders with ','.

New custom player command : HEAD (it places the item placed in the main hand of the player on his head)

New ExecutableItems command /ei take {playerName} {itemID} [quantity] (by default quantity = 1, to take the ExecutableItem in the inventory of the player )

New custom player command SENDCENTEREDMESSAGE {message} (it's like SENDMESSAGE but the message will be centered (with default chat settings of the client))