TVB-2870: Move everything related to monitors handling in a new class

Created by: VinczeRobert

Except the url handling (which I think it must stay in the controller) I moved everything else related to monitors (preparing the fragments and the monitor dict) in this one new class. I chose to send context instead of 4 params to handle_next_fragment_for_monitors, otherwise we woul end up with 10 parameters for that method and I wanted to avoid that many sent params.