Make it possible to log-in / reset passwords using the IceKey

[BjarniRunar]

The IceKey is better authentication than anything else we've got, including the e-mail confirmation. It makes sense to allow people to use it to log in and/or reset their password.

Although it would probably be too inconvenient to replace the login sequence with the IceKey, there is probably no reason to support e-mail based password resets (in the Icelandic environment) once we have this. Obviously we'd keep the old reset flow for the wider OSS community, but we shouldn't use it ourselves once the IceKey works.