Title: Add the cancel button for offers created by automatic offers
Summary: Once some offers are created by automatic offer function, these offers can't be cancelled.
Details: The lord set up automatic selling offers before winter comes, and some foods were put on the market. When winter comes, the region starts to starve but the lord can't withdraw the selling offers.
Benefits: Make the automatic offers more useful.
Possible Downsides/Exploits: None.
