Worksheet Import: User is prompted to enter the QR code if we can't detect it

[audionerd]

Electron doesn't support prompt so we'll need a custom ui for this feature.

• Can we make the QR code text easier to read/type? Zeros should look like zeros (currently could be confused for letter 'O'). Maybe avoid dots in the text?

• prevent menu shortcuts from taking over QR input (see: Can I make non global accelerators without putting things in a menu? electron/electron#1334)