qr code scanner: also accept images from clipboard and scan from them

[Simon-Laux]

Just a convenience feature, no need to mention it in the ui.

If you choose the option to paste from clipboard it should do the following:

1. try the text from clipboard as url
2. if that fails and there is an image in the clipboard scan the image and take the first detected qr code.

Why? I accidentally tried to do this multiple times already while not too thinking much, like I miss clicked one time trying to copy the link from the qr code at nine.testrun.org and I copied the image instead. I imagine there are multiple other ways to get into this situation. it is not much effort for us to make this work, so would be cool if it could.