Cards get detected multiple times

[Merovius]

Optimally, we wait until the card is removed, before we change the display back to default. Or something. This requires a bit of refactoring, but shouldn't be too hard.

[Merovius]

Note to self: Problem is:
• Card gets detected by polling goroutine, send over channell
• Received by main-goroutine, passed to HandleCard, which blocks
• Meanwhile, polling goroutine continues, detects the card a second time, sends over channel
• Send only succeds, after HandleCard stops blocking
Thus the card gets detected not more than twice, unless swiped very unnaturally for more than a second. Fix is to change the blocking-behaviour.