browser_side: follow changes made on quick_frontend for chat states and MUC symbols + minor fixes following the refactorisation: - some MUC handlers are no more needed, the presence handler is enough - move the chat states logic to quick_frontend - display MUC games symbols - remove classes contact_list.ContactsPanel, contact_panel.Occupant and contact_panel.OccupantsList - move buildPresenceStyle and setPresenceStyle to html_tools - fixes games menu callback