Random stuff that needs addressed
- flesh-out the bonus round feature.
- implement cascading reels + number-of-cascade-events-to-bonus option
- add more machine shapes/sizes: cocktail, tabletop and huge.
- add sounds
- Make infotext show casino name and machine balance.
- Make machines save itemstack meta only if they've been used or configured since placement
- Make it possible for owner to collect the money the machine earns from player losses (total money in minus total money out?)
- Add a cash-out machine, make slots' voucher screen give the user a voucher to feed it, instead of money.
- Make machines emit light, a little less than a torch, but configurable.
- Allow printing "." and discard unknown chars in both number-print routines. In number-to-words, if value is non-int, split at "." and read-out the decimal part separately from the integer part (e.g. "ONE HUNDRED TWENTY THREE POINT FOUR FIVE MINEGELD" or "ONE HUNDRED TWENTY THREE MINEGELD AND FORTY FIVE CENTS").
- In cash-out screen, display a proper error message if the balance is somehow negative.
- In balance display, just print "0" if negative.