Make a backup
While nothing will be deleted, it's always safe to have a backup while updating.

+ Added new serialization columns to multiple db tables. Auction house will try and convert existing items automatically and use the new method, if it fails it will fallback to the original method.
+ A bit more dev prep for the multi-currency stuff.
+ Fixed issue with placeholders in main menu for transaction button.
+ Added %auctionhouse_total_items_<bought/sold>% to PAPI placeholders.