Fixes for password checker from r70520:

Fixes for password checker from r70520:
* Removed the upper bound for brute force complexity checks
* Score for repetitions is now linear and is subtracted from brute force score to avoid overpenalizing long passwords
* Disabled checks by default for now, since many people consider them overly intrusive
* Made OutputPage::addPasswordSecurity() include jQuery just in case it's not already included
* Documented a little