Add Value Vintage format support

{"ops":[{"insert":"It would be pretty useful to have the option for Value Vintage as a format when designing a deck. I know there are problems with keeping constantly updating price information about decks so I'm guessing the simplest way would be to just keep the price fixed and then only check legality when the user presses optimise printings or something, then just keep a record of when the printings were last optimised (which might be useful on its own).\n"}]}