Sanitize URLs displayed in admin interface

Some of the sites I'm monitoring are behind basic HTTP authentication, and, as such, I've added usernames and passwords to the URLs (for example, "https://user:password@site.example.com/foo").

I've attached a patch that replaces the passwords in URLs with "..." when displayed various places in the admin interface. (I understand this doesn't add any serious security, since prod_monitor users can still get to the passwords by editing sites, but at least the passwords aren't blasted everywhere.)