Barcode detection in Web apps

Allow Objo Web applications to detect and read barcodes using the camera on the user's device, making the scanned text and detected format available to the application. The motivating use case is reading UPC-A product labels in a Web app opened on a phone, with interest in QR codes for future use.

Support camera selection and allow the application to save and request the user's preferred camera on later visits, subject to browser permissions and device availability. Investigate focus improvements where the device and browser provide suitable controls.