Add a convenience for selecting among settings, acordinging to setting
id, for easy examination.
Implement passcode cancellation from challenge screen, including:

- removal of passcode on cancellation, so user isn't continually locked
  out by forgotten passcode
- user notification of the removal when they next log in.
Instead of removing the account's passcode when the passcode challenge
is bypassed, offer the choice of removing it on the subsequent login to
that account.

Someone who bypasses the login screen should not have the prerogative to
remove that account's passcode.  By deferring that passcode removal
option to the next login to that account, we are referring the choice to
the authenticated account owner.