Limit how much a player can sell an item for on a sign and/or add confirmation

[TomLewis]

We have an issue with people tricking other players to click signs to drain their balance, having the option to limit the amount they can put on signs to target peoples balances would be handy.

[weaves7]

From #110; "I suggest popping up a book with a [buy] and [cancel] this way it's extremely obvious and in their face, we can also include in the book exactly what they are buying and for how much."