Bug 14168 - enhance streaming cataloging to include youtube

Bug 14168 - enhance streaming cataloging to include youtube

Add optional embedding of YouTube videos via HTML5Media.
New syspref: HTML5MediaYouTube: Embed/Don't embed videos.
Format WEBM is hardcoded as it is the only format accepted by all
modern browsers.

Test plan:
- apply patch
- catalogue a YouTube link in 856$u
- turn on HTML5MediaEnabled and HTML5MediaYouTube
- open the record in OPAC and staff client, check that the
  'Play media' tab is showing and playing the video works.

Possible enhancements for followups:
- check available formats, offer quality choice
- accept official YT URL shortener

Signed-off-by: Aleisha <aleishaamohia@hotmail.com>
Works perfectly!

Signed-off-by: Nicole C Engard <nengard@bywatersolutions.com>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
Signed-off-by: Brendan Gallagher brendan@bywatersolutions.com