Default to HTML5 player instead of Flash Player.

Also added support for YouTube's "enhanced privacy mode" and swapped the
player URLs to be protocol-relative.

Regex updated (as per Skizzerz's code review) to support various other,
valid YouTube URLs, including, but not limited to, youtu.be. See
http://linuxpanda.wordpress.com/2013/07/24/ultimate-best-regex-pattern-to-get-grab-parse-youtube-video-id-from-any-youtube-link-url/
for details about the regex.

This fixes http://bugzilla.shoutwiki.com/show_bug.cgi?id=249

Change-Id: I18ed1ce5928ab3395ab007d6fdb4dea6a98b15d9