Freetrading

- If player inventory can't hold offered items, deal will be canceled and related chat message will appear at both sides of a deal.

- If one of a players press "Seal a deal" while other not, GUI will show a lock for him and his partner. After "Seal a deal" is pressed player, who pressed that button, cannot alter offered items and money.

- Trade can be initiated only if player, who initiate trade, has no item in his main hand.