Util.Debug, Util.Info, Util.Warn, Util.Error routines instead of
direct calls to console.*. Add "logging=XXX" query variable that sets
the logging level (default is "warn").

Logging values:
    debug: code debug logging (many calls in performance path are also
           commented for performance reasons).
    info: informative messages including timing information.
    warn: significant events
    error: something has gone wrong