Saving & restoring video watching progress

Video progress updates:

- Mark as 'done' when 90% or more is watched.
- Keep 'done' flag when re-watching.

The video progress is stored on three events, whichever comes first:

- Every 30 seconds of video.
- Every 10% of the video.
- Every pause/stop/navigation to another page.
- When we detect the video is looping.

src/templates/projects/view.pug

@@ -74,6 +74,7 @@ link(rel="amphtml", href="{{ url_for('nodes.view', node_id=node._id, _external=T
 script(src="{{ url_for('static_pillar', filename='assets/js/vendor/videojs-6.2.8.min.js') }}")
 script(src="{{ url_for('static_pillar', filename='assets/js/vendor/videojs-ga-0.4.2.min.js') }}")
 script(src="{{ url_for('static_pillar', filename='assets/js/vendor/videojs-hotkeys-0.2.20.min.js') }}")
+script(src="{{ url_for('static_pillar', filename='assets/js/video_plugins.min.js') }}")
 | {% endblock %}
 
 | {% block css %}