Change barcode scanner app

Summary:
The old Barcode Scanner app is dead, switch the app to install on the device to Binary Eye (github.com/markusfisch/BinaryEye), which like this one is present on both F-Droid and Play Store. (Fix T1447)

If the device has no store app, open the link to the F-Droid page.

Also, change messages so they are nicer

Test Plan:
If there is NOT a system app for scanning QR which is impossible to remove:

• Remove all QR scanner apps on device
• Open app and tap on "Scan QR code"
• Say yes to the dialog
• Check that you land on Binary Eye app either on F-Droid or Play Store

Reviewers: Libre BusTO hackers, valerio.bozzolan

Reviewed By: Libre BusTO hackers, valerio.bozzolan

Subscribers: valerio.bozzolan

Project Tags: Libre BusTO

Maniphest Tasks: T1447

Differential Revision: https://gitpull.it/D244