Youtube features v2

Upgraded youtube video features for stories:
https://www.pivotaltracker.com/story/show/64993078
https://www.pivotaltracker.com/story/show/65429770
https://www.pivotaltracker.com/story/show/63372198

Minimised number of external requests to one per page
implemented filtering of videos by project tags and members
filtering is done both locally and at youtube api request