Remove use of stock_list outside store.c and ui-store.c
Only call store_stock_list() when the store contents change.
Keep accurate track of stock_num
Create a context to hold together store UI data
More display flags into store context
Remove store_knowledge global
Move menu instance inside context
Move scr_places arrays inside the context
Stop store_stock_list() assuming it's using something an array inside struct store
Only keep an array version of store stock when useful for the UI
s/menu_type/struct menu/
Remove ENTER_STORE command, fix some externs