Support Barcode Scanners

[panzi]

For some applications it would be really handy if there would be a mode where it wouldn't use a camera at all, but just provide an input field where you can paste the scanned qr-code. E.g. when people already have an USB QR-code scanner that device basically just types out what you scan. So you just click into the input box and then scan one QR-code after another and the app displays what you've last scanned.

I think this might be really easy to implement and would be really helpful for organizations that already have lots of QR-code scanners connected to desktop PCs, but that don't have mobile phones or web cams.