add interface for popularity statistics

- reordered helper components
- rebuild old statistics interface.
- add line and pie charts support
- allow selecting data in curtain time interval
- more..
cleanup duplicate code popularity
apply time filtering to max count as well

the join for max count is very very slow..
close session and avoid unneccessary query
added documentation popularity
more documentation popularity
Merge branch 'popularitystats' of git://github.com/Klap-in/dokuwiki-plugin-pluginrepo into pull-request-69

* 'popularitystats' of git://github.com/Klap-in/dokuwiki-plugin-pluginrepo:
  more documentation popularity
  added documentation popularity
  close session and avoid unneccessary query
  apply time filtering to max count as well
  cleanup duplicate code popularity
  add interface for popularity statistics
optimize date filtering by extending the popularity table