This avoids the need to list newly-added classes in multiple places
(which could be extended to the search plugin) and gets rid of a few
ugly macros, along with a few other minor changes.
* New option: trade-select-all: Prompts when selecting all goods
when some goods are already selected
* Improved trade confirmation message depending on selected goods
* Made seize and offer confirmations only display when goods in the
appropriate columns are selected
* States of each option are now listed by "confirm help"
lethosor