Add features needed for displaying the registration code and a list of RAs on screen in the Self-Service, and include a list of RAs in the registration mail.

 - Add ability to search by verified second factor ID.
 - Add ability to search unverified second factor by verification nonce.
 - Add registration authority list resource.
 - Include a list of RAs in the registration e-mail.
Beep-beep @DRvanR.