QR code improvements for Kin wallet backup/restore

details filed in this issue for the old SDK:
* https://github.com/kinecosystem/kin-sdk-android/issues/78

tl;dr
* wallet restore uses a QR code
* users occasionally screenshot the QR code, and it has all the info encoded, but restore process does not allow a screenshot to be used

would be great to add this into the new SDKs