Allow multiple cards to be loaded directly into slots KK/KKS

[Timo713]

Allow multiple cards to be loaded into different slots in studio and the main game.

In studio, dragging and dropping multiple cards only loads one of the cards selected if there's no slots, if there's multiple slots, it will load the same card on all the slots, which is fine for one card, but not when you want to load multiple cards at once.

Meanwhile, in the character selection screen in the main game and H modes, dragging cards doesn't work. There is a button in the main game and H mode to load random cards and fill empty slots, but it would be great if you could fill those slots with cards you want by just dragging them.

This is more of an improvement than a bug, possibly a difficult one if it hasn't been implemented yet, but it would greatly help loading cards in the game for some.

[ManlyMarco]

It's a good idea. Problem is it will require some nontrivial changes since currently everything assumes a single card at a time.