[FIX] Fit inner timetable
[FIX] Fit inner timetable

  - 'Fit inner timetable' button did't resize the first session slot to
    the length of the whole session;
  - when adding, removing or resizing slot belonging to a session, the
    session times are changed properly (method fit() is executed at the
    end of those operations);
  - deprecated method _enableSessionSlots now always returns True;
  - parts of code using deprecated variables/methods were commented out;
  - fixes #316

mic4ael/indico,pferreir/indico,ThiefMaster/indico,mvidalgarcia/indico,pferreir/indico,DirkHoffmann/indico,DirkHoffmann/indico,ThiefMaster/indico,ThiefMaster/indico,OmeGak/indico,mic4ael/indico,ThiefMaster/indico,mic4ael/indico,OmeGak/indico,pferreir/indico,indico/indico,indico/indico,DirkHoffmann/indico,mvidalgarcia/indico,mic4ael/indico,DirkHoffmann/indico,indico/indico,pferreir/indico,mvidalgarcia/indico,OmeGak/indico,indico/indico,mvidalgarcia/indico,OmeGak/indico