Add vending machine support

[MaxVandenbussche]

Cool BAB improvement below:

An obstacle in making a vending machine is dealing with money. Proofing money, giving money back, ... Linking BAB to the vending machine hardware could solve these problems.
A possible scenario:

1. Add stuff for sale at the vending machine into BAB.
2. User purchases something in BAB and pays with the payment methods already present in BAB.
3. BAB creates unique one-time-use code.
4. User enters code into the vending machine keypad.
5. The vending machine authenticates code with BAB and dispenses the purchase.

Nice side-effect is that all sales and revenue are traceable in BAB.
Hardware/software implementation in vending machine would be very doable.