issue2550949: Rate limit password guesses/login attempts. Generic rate limit mechanism added. Deployed for web page logins. Default is 3 login attempts/minute for a user. After which one login attempt every 20 seconds can be done. Uses gcra algorithm so all I need to store is a username and timestamp in the one time key database. This does mean I don't have a list of all failed login attempts as part of the rate limiter. Set up config setting as well so admin can tune the rate. Maybe 1 every 10 seconds is ok at a site with poor typists who need 6 attempts to get the password right 8-). The gcra method can also be used to limit the rest and xmlrpc interfaces if needed. The mechanism I added also supplies a status method that calculates the expected values for http headers returned as part of rate limiting. Also tests added to test all code paths I hope.

def audit_html_files(db, cl, nodeid, newvalues):
    if 'type' in newvalues and newvalues['type'] == 'text/html':
        newvalues['type'] = 'text/plain'
    

def init(db):
    db.file.audit('set', audit_html_files)
    db.file.audit('create', audit_html_files)