monitoring/list: no need to declare $this->backend

This happens in the monitoring base controller right now
monitoring/list: make use of new params

This brings our lists back to life and makes our filters work again.
Monitoring\Object: replace fromRequest with params

This is only a temporary solution, the Monitoring\Object should be
fetched from the backend created in our front controller.
Monitoring\Object\Host: explicit WHERE

Related to the former commit, no more auto-voodoo