Add "give" signs to actionsigns

"items" is a list of items to give the user.  Each item may have a description, and/or a single comment can be left to say to the player after all items have been delivered.

Format:
--------

    - coordinates: [x, y, z]
      type: give
      items:
      - give_item: 2
        give_item_data: 0          [default: 0]
        give_item_amount: 1        [default: 1]
        give_item_desc: one grass  [default: null]
      - give_item: 276
        give_item_data: 0
        give_item_amount: 1
        give_item_desc: a sword
      comment: You get a car!      [default: null]