Refactor statistics

I made a new controller to handle statistics. The old statistics have been moved in that controller and a new action has been added to display idle feeds. I also added a menu in the left panel to navigate between the statistics pages.
See #90

This a work in progress. Please comment to see if I continue in that direction.
Because I want to get rid of that action. I just copied it from the previous version so we don't loose anything.