add video duration to events

common/lib/xmodule/xmodule/js/fixtures/video_hls.html

common/lib/xmodule/xmodule/js/fixtures/video_html5.html

...xmodule/xmodule/js/spec/video/video_events_plugin_spec.js

...on/lib/xmodule/xmodule/js/spec/video/video_player_spec.js

common/lib/xmodule/xmodule/js/src/video/01_initialize.js

common/lib/xmodule/xmodule/js/src/video/03_video_player.js

common/lib/xmodule/xmodule/js/src/video/09_events_plugin.js

common/lib/xmodule/xmodule/video_module/video_module.py

lms/djangoapps/courseware/tests/test_video_mongo.py