Implements #12, TOTP. This adds support for TOTP to the api and server, with server side token generation, authentication and the correct URI for encoding into QR codes for client token addition. Some extra measures have been taken such as in the stepped auth to always notify on the success or failure of the TOTP first (regardless of order) to prevent PW bruteforce attacks.
Implements #122 password import. This adds most of the server core framework to allow password imports from other sources, with new types easily able to be added in credential.rs.
