Munin contributed plugins

http_request_time: document the timeout option

make timeouts customizable

Improve the HTTP plugin by allowing configuring a proxy and friendly name per URL.

Note that the configuration file syntax has changed. You need one "url"
variable per URL now, numbered starting with 1, e.g. url1, url2, url3.
Each one can be configured by suffixing its variable, e.g. url1_proxy,...