Feature request: add sharing capabilities

[hadacnot]

It would be easier for the user to share the QR code as an image, and to be able to share, from other Android apps, a QR image with the QRL app.

A) add a "Share with" button on the Send page that copies the QR, not the address, as an image, and allows to publish it on other Android apps that can receive images.

B) add the possibility for the QRL app to receive images, so that it appears in the usual Android list when you Share an image from other apps. The QRL app in that case should open directly in the Send view, and try to recover an address from the image