Allow export/import of ResidentKey

[aryasenna]

Please consider adding (encrypted) export/import a la OpenPGP app.
So when we (inevitably) upgrade the firmware or the app, we won't have to re-register to dozens of site.

Related discussion: LedgerHQ/app-u2f#3 (comment)

[My1]

Please consider adding (encrypted) export/import a la OpenPGP app. So when we (inevitably) upgrade the firmware or the app, we won't have to re-register to dozens of site.

Related discussion: LedgerHQ/app-u2f#3 (comment)

If resident keys work on ledger simply by storing the credential IDs, ledger could do just that, and export the credential IDs