Add notifications for trades

Please add an option to enable notifications for trade activity - offer received, response received, trade agreement reached, trade declined.

The long duration allowed for responses combined with fact that only one trade can be executed at a time means that a a player can be locked up in a single trade for several days. Adding notifications would greatly reduce turn around time and increase the number of successful trades possible. Ideally whether a player has trade notifications enabled would also be visible to trading partners so you could choose not to trade with a friend that has notifications disabled.