MDL-41031 events: Add a base class for content view
MDL-40052 events: Add page view event for report_participation
MDL-40052 events: Add page view event for report_log
MDL-40052 events: Add page view event for report_stats
MDL-40052 events: Add page view event for report_outline
MDL-40052 events: Add page view event for report_loglive
MDL-40052 events: Coding style improvments