Log failed login attemps, related to Feature #432 (try 2)

Try 2, using user_error instead of a direct call to Logger.

Concerning schema concerns raised by gothfox, about updating from an older schema, and causing a failure when using Logger: the schema version is already checked within the SQL Logger (see patch https://github.com/gothfox/Tiny-Tiny-RSS/commit/512b7793917230e37e47e9a68a243053189cb846), which is IMHO the place for this kind of checks. So this issue is already taken care of.