Require password for certain features

[jace]

Creating new applications, adding/deleting organizations and other such critical actions should require a password prompt. However, since Lastuser doesn't require a password to login if the account is linked to external ids, this should be amended too.

1. When accessing a critical feature, ask for a password. Remember this for up to 15 minutes.
2. If the user does not have a password, require them to set a password before they can proceed.
3. Provide an option in the profile setting that requires a password at all times. This setting can be enabled only if they have at least one verified email address.

[jace]

UserSession introduced a sudo_enabled_at column with a has_sudo property and set_sudo method in 0b9b07bc29e5ba6cccaaed407c99e54367f7ea68 for #89.

[jace]

The has_sudo method from #89 is hardcoded to a 1 hour timedelta, not 15 minutes as per this ticket. We should revisit during implementation of this ticket.

[jace]

This was originally discussed in #5.