The access log filter allows the access log to be filtered by a status
code pattern. The pattern is a list of strings of the form `NXX`. At
least one number must be specified and up to 2 Xs can be used. That
means the filter can be an exact status code or it can be a range of
them. For example, `500` would only match the 500 http status code while
`5XX` would match any status code beginning with the number 5
(categorized as server errors). The pattern `50X` would also be
accepted. Both uppercase and lowercase Xs are allowed.
Multiple filters can be specified and the log line will be printed if
one of them matches. If there are no filters specified, all status codes
are printed.
Normalize the output for the various help options so they all follow the
same format and display all relevant options.
Removing some of the unused config options from the configuration file
and updating the help documentation. Removing some remaining references
to clustering within the open source version.