Clean up multibuy a bit & add an autobuy button to the badge item welcome panel

[Prommah]

With multibuy, there's no need to add the old TrySpendBadgePoints function back onto the scene object to be able to access 'this', you just have to call it with trt_oldbuy.call instead, which seems cleaner.

Also added a third parameter to the replacement of TrySpendBadgePoints which will skip the multibuy popup logic. Without that, any purchase of a single item from the autobuy script will cause a popup as if the user clicked the item themselves.

With that in place, added an autobuy button which will buy 1 Like New for every 10 Wormholes, then Raining Gold, then Treasure, and one Pumped Up if there's a point left over. It does this efficiently without looping until there are no points left. Instead, it just buys each item in a single batch. It also works off of the prices given on the welcome panel instead of hard-coded values (just in case they change or something).

[wchill]

tested?

[Prommah]

I tested it at the time out of the game and then in-game with a few thousand badge points and it worked great. Just tested my changes in-game now with 4.8.2 and >830k points, they appear to still work without any problems. (7546 Wormholes and 754 Like New purchased)