Label the xs property properly in ip_email_record.js
Rename the variable that keeps track of login failures

While it's similar in the way it's handled to the one keeping track
of emails sent, it keeps track of something different so it should
have a different name to avoid confusion.
Account lockout when there are way too many attempts for an email

This is a global limit which applies to a given email address
regardless of the user agent's IP address.