qml: add signals for QEQRScanner and fallbacks, add QEBytes container type
so we can pass along byte arrays between QML and python, port qr scan
occurrences to new signals.
When putting app to background with qr scanner active, then moved to foreground again,
SimpleScannerActivity instance is not destroyed, but the local mScannerView was re-initialized
with a new instance (through startCamera()) regardless of pre-existing instance, and added to
the contentFrame. This leaves the previous mScannerView instance in limbo, potentially getting
garbage collected at unpredictable times.
Replaces the unmaintained and unreliable
`me.dm7.barcodescanner:zxing:1.9.8` qr code scanning library used only
on android with the `com.github.markusfisch:BarcodeScannerView:1.6.0`
(https://github.com/markusfisch/BarcodeScannerView) library which seems
more actively maintained.
The `BarcodeScannerView` library is incredibly fast and scanning qr
codes is now fun again :)
wip: still looking into ways to pin the library.
