2dos/potential improvements:
* zodbcache: total objects should be an extra graph
* zopethreads: should the thread used for the munin view count or not? :)
* zopethreads: known helper thread (clockserver, squidtool) could be reported separately
* gocept.munin should be extended to support munin's '.draw' & '.info' parameters,
  see http://muninexchange.projects.linpro.no/?view&phid=339
* plugin: average response times
* plugin: site error count
* plugin: conflict error count
