[DevKit] POS System API - implement support for ReceiptRequest.cbTerminalID in lib and HOWTOs to demonstrate proper receipt routing

[turtletramp]

When is receipt routing proper:

• a receipt is usually only to be show on a single target device and not on all
  • Retail where usually the InStore App is on a terminal next to the stationary POS so it should only show on the terminal next to that POS; payment may be done on the same terminal or on another
  • Hospitality: Usually used on mobile devices where first a payment transaction is done on the same device where later also the receipt is shown

TODO:

• In howto every request should be sent to a target cbTerminalID by first asking the user to enter one and if they do not enter any default "term1" is used
• check if we somewhere should update the docs

Nothing TODO on:

• As per default the InStore App has an empty cbTerminalID configured they will still react on the request -> nothing to do there