Updated authenticator TOTP

- Added security check for previouse used codes
- Allow TOTP codes with 1 step back and forward when there is a time
drift. This means in total 3 codes could be valid. But only newer codes
then the previouse used codes are excepted after that.

migrations/mysql/2019-10-10-083032_add_column_to_twofactor/up.sql

@@ -0,0 +1 @@
+ALTER TABLE twofactor ADD COLUMN last_used INTEGER NOT NULL DEFAULT 0;